A vulnerability in the SSH server of Cisco Adaptive Security Appliance (ASA) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition for the SSH server of an affected device. This vulnerability is due to a logic error when an SSH session is established. An attacker could exploit this vulnerability by sending crafted SSH messages to an affected device. A successful exploit could allow the attacker to exhaust available SSH resources on the affected device so that new SSH connections to the device are denied, resulting in a DoS condition. Existing SSH connections to the device would continue to function normally. The device must be rebooted manually to recover. However, user traffic would not be impacted and could be managed using a remote application such as Cisco Adaptive Security Device Manager (ASDM).

Cisco Web Security Appliance (WSA) 8.0.7 allows remote HTTP servers to cause a denial of service (memory consumption from stale TCP connections) via crafted responses, aka Bug ID CSCuw10426.

A vulnerability in the DHCP version 4 (DHCPv4) server feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to trigger a crash of the dhcpd process, resulting in a denial of service (DoS) condition. This vulnerability exists because certain DHCPv4 messages are improperly validated when they are processed by an affected device. An attacker could exploit this vulnerability by sending a malformed DHCPv4 message to an affected device. A successful exploit could allow the attacker to cause a crash of the dhcpd process. While the dhcpd process is restarting, which may take approximately two minutes, DHCPv4 server services are unavailable on the affected device. This could temporarily prevent network access to clients that join the network during that time period and rely on the DHCPv4 server of the affected device. Notes: Only the dhcpd process crashes and eventually restarts automatically. The router does not reload. This vulnerability only applies to DHCPv4. DHCP version 6 (DHCPv6) is not affected.

A vulnerability in the IPsec Manager of Cisco StarOS for Cisco Aggregation Services Router (ASR) 5000 Series Routers and Virtualized Packet Core (VPC) System Software could allow an unauthenticated, remote attacker to terminate all active IPsec VPN tunnels and prevent new tunnels from being established, resulting in a denial of service (DoS) condition. The vulnerability is due to improper processing of corrupted Internet Key Exchange Version 2 (IKEv2) messages. An attacker could exploit this vulnerability by sending crafted IKEv2 messages toward an affected router. A successful exploit could allow the attacker to cause the ipsecmgr service to reload. A reload of this service could cause all IPsec VPN tunnels to be terminated and prevent new tunnels from being established until the service has restarted, resulting in a DoS condition. This vulnerability affects the following Cisco products when they are running Cisco StarOS: Cisco Aggregation Services Router (ASR) 5000 Series Routers, Virtualized Packet Core (VPC) System Software. Cisco Bug IDs: CSCve29605.

Cisco AsyncOS on Email Security Appliance (ESA) devices with software 8.5.6-073, 8.5.6-074, and 9.0.0-461, when clustering is enabled, allows remote attackers to cause a denial of service (clustering and SSH outage) via a packet flood, aka Bug IDs CSCur13704 and CSCuq05636.

A vulnerability in the SSH service of Cisco Catalyst SD-WAN Manager could allow an unauthenticated, remote attacker to cause a process crash, resulting in a DoS condition for SSH access only. This vulnerability does not prevent the system from continuing to function, and web UI access is not affected. This vulnerability is due to insufficient resource management when an affected system is in an error condition. An attacker could exploit this vulnerability by sending malicious traffic to the affected system. A successful exploit could allow the attacker to cause the SSH process to crash and restart, resulting in a DoS condition for the SSH service.

A vulnerability in the nginx configurations that are provided as part of the VPN-less reverse proxy for Cisco Finesse could allow an unauthenticated, remote attacker to create a denial of service (DoS) condition for new and existing users who are connected through a load balancer. This vulnerability is due to improper IP address filtering by the reverse proxy. An attacker could exploit this vulnerability by sending a series of unauthenticated requests to the reverse proxy. A successful exploit could allow the attacker to cause all current traffic and subsequent requests to the reverse proxy through a load balancer to be dropped, resulting in a DoS condition.

A vulnerability in the implementation of Border Gateway Protocol (BGP) Ethernet VPN (EVPN) functionality in Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to incorrect processing of a BGP update message that contains crafted EVPN attributes. An attacker could indirectly exploit the vulnerability by sending BGP EVPN update messages with a specific, malformed attribute to an affected system and waiting for a user on the device to display the EVPN operational routes’ status. If successful, the attacker could cause the BGP process to restart unexpectedly, resulting in a DoS condition. The Cisco implementation of BGP accepts incoming BGP traffic only from explicitly defined peers. To exploit this vulnerability, the malicious BGP update message would need to come from a configured, valid BGP peer, or would need to be injected by the attacker into the victim's BGP network on an existing, valid TCP connection to a BGP peer.

IP-in-IP protocol specifies IP Encapsulation within IP standard (RFC 2003, STD 1) that decapsulate and route IP-in-IP traffic is vulnerable to spoofing, access-control bypass and other unexpected behavior due to the lack of validation to verify network packets before decapsulation and routing.

A vulnerability in the IP Service Level Agreements (IP SLA) responder and Two-Way Active Measurement Protocol (TWAMP) features of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause device packet memory to become exhausted or cause the IP SLA process to crash, resulting in a denial of service (DoS) condition. This vulnerability exists because socket creation failures are mishandled during the IP SLA and TWAMP processes. An attacker could exploit this vulnerability by sending specific IP SLA or TWAMP packets to an affected device. A successful exploit could allow the attacker to exhaust the packet memory, which will impact other processes, such as routing protocols, or crash the IP SLA process.

A vulnerability in the HTTP server code of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause the HTTP server to crash. The vulnerability is due to a logical error in the logging mechanism. An attacker could exploit this vulnerability by generating a high amount of long-lived connections to the HTTP service on the device. A successful exploit could allow the attacker to cause the HTTP server to crash.

A vulnerability in the WebVPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause increased CPU utilization on an affected device. The vulnerability is due to excessive processing load for a specific WebVPN HTTP page request. An attacker could exploit this vulnerability by sending multiple WebVPN HTTP page load requests for a specific URL. A successful exploit could allow the attacker to increase CPU load on the device, resulting in a denial of service (DoS) condition, which could cause traffic to be delayed through the device.

A vulnerability in the Cisco IOx application hosting environment of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause the Cisco IOx application hosting environment to stop responding, resulting in a denial of service (DoS) condition. This vulnerability is due to the improper handling of HTTP requests. An attacker could exploit this vulnerability by sending crafted HTTP requests to an affected device. A successful exploit could allow the attacker to cause the Cisco IOx application hosting environment to stop responding. The IOx process will need to be manually restarted to recover services.

A vulnerability in the system resource management of Cisco Elastic Services Controller (ESC) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) to the health monitor API on an affected device. The vulnerability is due to inadequate provisioning of kernel parameters for the maximum number of TCP connections and SYN backlog. An attacker could exploit this vulnerability by sending a flood of crafted TCP packets to an affected device. A successful exploit could allow the attacker to block TCP listening ports that are used by the health monitor API. This vulnerability only affects customers who use the health monitor API.

A vulnerability in the Common Open Policy Service (COPS) of Cisco IOS XE Software for Cisco cBR-8 Converged Broadband Routers could allow an unauthenticated, remote attacker to cause resource exhaustion, resulting in a denial of service (DoS) condition. This vulnerability is due to a deadlock condition in the code when processing COPS packets under certain conditions. An attacker could exploit this vulnerability by sending COPS packets with high burst rates to an affected device. A successful exploit could allow the attacker to cause the CPU to consume excessive resources, which prevents other control plane processes from obtaining resources and results in a DoS.

A vulnerability in the SSH service of the Cisco StarOS operating system could allow an unauthenticated, remote attacker to cause an affected device to stop processing traffic, resulting in a denial of service (DoS) condition. The vulnerability is due to a logic error that may occur under specific traffic conditions. An attacker could exploit this vulnerability by sending a series of crafted packets to an affected device. A successful exploit could allow the attacker to prevent the targeted service from receiving any traffic, which would lead to a DoS condition on the affected device.

A vulnerability in the web UI of Cisco Umbrella could allow an unauthenticated, remote attacker to negatively affect the performance of this service. The vulnerability exists due to insufficient rate limiting controls in the web UI. An attacker could exploit this vulnerability by sending crafted HTTPS packets at a high and sustained rate. A successful exploit could allow the attacker to negatively affect the performance of the web UI. Cisco has addressed this vulnerability.

A vulnerability in ICMP Version 6 (ICMPv6) processing in Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a slow system memory leak, which over time could lead to a denial of service (DoS) condition. This vulnerability is due to improper error handling when an IPv6-configured interface receives a specific type of ICMPv6 packet. An attacker could exploit this vulnerability by sending a sustained rate of crafted ICMPv6 packets to a local IPv6 address on a targeted device. A successful exploit could allow the attacker to cause a system memory leak in the ICMPv6 process on the device. As a result, the ICMPv6 process could run out of system memory and stop processing traffic. The device could then drop all ICMPv6 packets, causing traffic instability on the device. Restoring device functionality would require a device reboot.

A vulnerability in the Cisco IOx Application Framework of Cisco 809 Industrial Integrated Services Routers (Industrial ISRs), Cisco 829 Industrial ISRs, Cisco CGR 1000 Compute Module, and Cisco IC3000 Industrial Compute Gateway could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient error handling during packet processing. An attacker could exploit this vulnerability by sending a high and sustained rate of crafted TCP traffic to the IOx web server on an affected device. A successful exploit could allow the attacker to cause the IOx web server to stop processing requests, resulting in a DoS condition.

A vulnerability in the ingress traffic manager of Cisco IOS XE Software for Cisco Network Convergence System (NCS) 520 Routers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition in the web management interface of an affected device. This vulnerability is due to incorrect processing of certain IPv4 TCP traffic that is destined to an affected device. An attacker could exploit this vulnerability by sending a large number of crafted TCP packets to the affected device. A successful exploit could allow the attacker to cause the web management interface to become unavailable, resulting in a DoS condition. Note: This vulnerability does not impact traffic that is going through the device or going to the Management Ethernet interface of the device.

A vulnerability in the implementation of the system login block-for command for Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a login process to unexpectedly restart, causing a denial of service (DoS) condition. This vulnerability is due to a logic error in the implementation of the system login block-for command when an attack is detected and acted upon. An attacker could exploit this vulnerability by performing a brute-force login attack on an affected device. A successful exploit could allow the attacker to cause a login process to reload, which could result in a delay during authentication to the affected device.

A vulnerability in the Java Management Extensions (JMX) component of Cisco Unified Communications Manager (Unified CM) and Cisco Unified Communications Manager Session Management Edition (Unified CM SME) could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on an affected system. This vulnerability is due to an unsecured TCP/IP port. An attacker could exploit this vulnerability by accessing the port and restarting the JMX process. A successful exploit could allow the attacker to cause a DoS condition on an affected system.

A vulnerability in the VXLAN Operation, Administration, and Maintenance (OAM) feature of Cisco NX-OS Software, known as NGOAM, could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of specific packets with a Transparent Interconnection of Lots of Links (TRILL) OAM EtherType. An attacker could exploit this vulnerability by sending crafted packets, including the TRILL OAM EtherType of 0x8902, to a device that is part of a VXLAN Ethernet VPN (EVPN) fabric. A successful exploit could allow the attacker to cause an affected device to experience high CPU usage and consume excessive system resources, which may result in overall control plane instability and cause the affected device to reload. Note: The NGOAM feature is disabled by default.

A vulnerability in the Cisco AnyConnect VPN server of Cisco Meraki MX and Cisco Meraki Z Series Teleworker Gateway devices could allow an unauthenticated, remote attacker to cause a DoS condition for targeted users of the AnyConnect service on an affected device. This vulnerability is due to insufficient entropy for handlers that are used during SSL VPN session establishment. An unauthenticated attacker could exploit this vulnerability by brute forcing valid session handlers. An authenticated attacker could exploit this vulnerability by connecting to the AnyConnect VPN service of an affected device to retrieve a valid session handler and, based on that handler, predict further valid session handlers. The attacker would then send a crafted HTTPS request using the brute-forced or predicted session handler to the AnyConnect VPN server of the device. A successful exploit could allow the attacker to terminate targeted SSL VPN sessions, forcing remote users to initiate new VPN connections and reauthenticate.

A vulnerability in the login authentication functionality of the Remote Access SSL VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to deny further VPN user authentications for several minutes, resulting in a temporary denial of service (DoS) condition. This vulnerability is due to ineffective handling of memory resources during the authentication process. An attacker could exploit this vulnerability by sending crafted packets, which could cause resource exhaustion of the authentication process. A successful exploit could allow the attacker to deny authentication for Remote Access SSL VPN users for several minutes, resulting in a temporary DoS condition.

A vulnerability in system resource management in Cisco UCS 6400 and 6500 Series Fabric Interconnects that are in Intersight Managed Mode (IMM) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on the Device Console UI of an affected device. This vulnerability is due to insufficient rate-limiting of TCP connections to an affected device. An attacker could exploit this vulnerability by sending a high number of TCP packets to the Device Console UI. A successful exploit could allow an attacker to cause the Device Console UI process to crash, resulting in a DoS condition. A manual reload of the fabric interconnect is needed to restore complete functionality.

A vulnerability in the Dedicated XML Agent feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) on XML TCP listen port 38751. This vulnerability is due to a lack of proper error validation of ingress XML packets. An attacker could exploit this vulnerability by sending a sustained, crafted stream of XML traffic to a targeted device. A successful exploit could allow the attacker to cause XML TCP port 38751 to become unreachable while the attack traffic persists.

The authentication manager process in the web framework in Cisco Intrusion Prevention System (IPS) does not properly handle user tokens, which allows remote attackers to cause a denial of service (intermittent MainApp hang) via a crafted management-interface connection request, aka Bug ID CSCuf20148.

The OSPFv3 functionality in Cisco IOS XR 5.1 allows remote attackers to cause a denial of service (process crash) via a malformed LSA Type-1 packet, aka Bug ID CSCuj82176.

Memory leak in the connection-manager implementation in Cisco Adaptive Security Appliance (ASA) Software 9.1(.3) and earlier allows remote attackers to cause a denial of service (multi-protocol management outage) by making multiple management session requests, aka Bug ID CSCug33233.

Cisco Unified Communications Manager (aka CUCM or Unified CM) allows remote attackers to cause a denial of service (service restart) via a crafted SIP message, aka Bug ID CSCub54349.

The protocol-inspection feature on Cisco Adaptive Security Appliances (ASA) devices does not properly implement the idle timeout, which allows remote attackers to cause a denial of service (connection-table exhaustion) via crafted requests that use an inspected protocol, aka Bug ID CSCuh13899.

Multiple vulnerabilities exist in the Cisco Webex Network Recording Player for Advanced Recording Format (ARF) and Webex Recording Format (WRF) files. An attacker could exploit these vulnerabilities by providing a user with a malicious .arf or .wrf file via email or URL and convincing the user to launch the file in the Webex recording players. Exploitation of these vulnerabilities could cause an affected player to crash, resulting in a denial of service (DoS) condition. The Cisco Webex players are applications that are used to play back Webex meetings that have been recorded by an online meeting attendee. The Webex Network Recording Player for .arf files can be automatically installed when the user accesses a recording that is hosted on a Webex server. The Webex Player for .wrf files can be downloaded manually. These vulnerabilities affect ARF and WRF recording players available from Cisco Webex Meetings Suite sites, Cisco Webex Meetings Online sites, and Cisco Webex Meetings Server. Cisco Bug IDs: CSCvh70253, CSCvh70268, CSCvh72272, CSCvh72281, CSCvh72285, CSCvi60477, CSCvi60485, CSCvi60490, CSCvi60520, CSCvi60529, CSCvi60533.

A vulnerability in the Secure Sockets Layer (SSL) Engine of Cisco Firepower System Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to improper error handling while processing SSL traffic. An attacker could exploit this vulnerability by sending a large volume of crafted SSL traffic to the vulnerable device. A successful exploit could allow the attacker to degrade the device performance by triggering a persistent high CPU utilization condition. Cisco Bug IDs: CSCvh89340.

A vulnerability in the Cisco Discovery Protocol functionality of Cisco ATA 190 Series Analog Telephone Adapter firmware could allow an unauthenticated, remote attacker to execute arbitrary code on an affected device and cause Cisco Discovery Protocol service to restart. This vulnerability is due to missing length validation of certain Cisco Discovery Protocol packet header fields. An attacker could exploit these vulnerabilities by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to execute code on the affected device and cause Cisco Discovery Protocol to restart unexpectedly, resulting in a DoS condition.

A vulnerability in a feature that monitors RADIUS requests on Cisco Identity Services Engine (ISE) Software could allow an unauthenticated, remote attacker to negatively affect the performance of an affected device. This vulnerability is due to insufficient management of system resources. An attacker could exploit this vulnerability by taking actions that cause Cisco ISE Software to receive specific RADIUS traffic. A successful and sustained exploit of this vulnerability could allow the attacker to cause reduced performance of the affected device, resulting in significant delays to RADIUS authentications. There are workarounds that address this vulnerability.

A vulnerability in SMART-SSL Accelerator functionality for Cisco Wide Area Application Services (WAAS) 6.2.1, 6.2.1a, and 6.2.3a could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition where the WAN optimization could stop functioning while the process restarts. The vulnerability is due to a Secure Sockets Layer/Transport Layer Security (SSL/TLS) alert being incorrectly handled when in a specific SSL/TLS connection state. An attacker could exploit this vulnerability by establishing a SMART-SSL connection through the targeted device. The attacker would then send a crafted stream of SSL/TLS traffic. An exploit could allow the attacker to cause a DoS condition where WAN optimization could stop processing traffic for a short period of time. Cisco Bug IDs: CSCvb71133.

A Denial of Service vulnerability in the Telnet remote login functionality of Cisco NX-OS Software running on Cisco Nexus 9000 Series Switches could allow an unauthenticated, remote attacker to cause a Telnet process used for login to terminate unexpectedly and the login attempt to fail. There is no impact to user traffic flowing through the device. Affected Products: This vulnerability affects Cisco Nexus 9000 Series Switches that are running Cisco NX-OS Software and are configured to allow remote Telnet connections to the device. More Information: CSCux46778. Known Affected Releases: 7.0(3)I3(0.170). Known Fixed Releases: 7.0(3)I3(1) 7.0(3)I3(0.257) 7.0(3)I3(0.255) 7.0(3)I2(2e) 7.0(3)F1(1.22) 7.0(3)F1(1).

A Denial of Service vulnerability in the remote login functionality for Cisco NX-OS Software running on Cisco Nexus 9000 Series Switches could allow an unauthenticated, remote attacker to cause a process used for login to terminate unexpectedly and the login attempt to fail. There is no impact to user traffic flowing through the device. The attacker could use either a Telnet or an SSH client for the remote login attempt. Affected Products: This vulnerability affects Cisco Nexus 9000 Series Switches that are running Cisco NX-OS Software and are configured to allow remote Telnet connections to the device. More Information: CSCuy25824. Known Affected Releases: 7.0(3)I3(1) 8.3(0)CV(0.342) 8.3(0)CV(0.345). Known Fixed Releases: 8.3(0)CV(0.362) 8.0(1) 7.0(3)IED5(0.19) 7.0(3)IED5(0) 7.0(3)I4(1) 7.0(3)I4(0.8) 7.0(3)I2(2e) 7.0(3)F1(1.22) 7.0(3)F1(1) 7.0(3)F1(0.230).

A vulnerability in the TCP normalizer of Cisco Adaptive Security Appliance (ASA) Software (8.0 through 8.7 and 9.0 through 9.6) and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause Cisco ASA and FTD to drop any further incoming traffic on all interfaces, resulting in a denial of service (DoS) condition. The vulnerability is due to improper limitation of the global out-of-order TCP queue for specific block sizes. An attacker could exploit this vulnerability by sending a large number of unique permitted TCP connections with out-of-order segments. An exploit could allow the attacker to exhaust available blocks in the global out-of-order TCP queue, causing the dropping of any further incoming traffic on all interfaces and resulting in a DoS condition. Cisco Bug IDs: CSCvb46321.

Cisco WebEx Meetings Player T29.10, when WRF file support is enabled, allows remote attackers to cause a denial of service (application crash) via a crafted file, aka Bug ID CSCuz80455.

A vulnerability in the network stack of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability exists because the software improperly releases resources when it processes certain IPv6 packets that are destined to an affected device. An attacker could exploit this vulnerability by sending multiple crafted IPv6 packets to an affected device. A successful exploit could cause the network stack to run out of available buffers, impairing operations of control plane and management plane protocols and resulting in a DoS condition. Manual intervention would be required to restore normal operations on the affected device. For more information about the impact of this vulnerability, see the Details section of this advisory.

A vulnerability in the ipsecmgr process of Cisco ASR 5000 Series Software (StarOS) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. This vulnerability is due to insufficient validation of incoming Internet Key Exchange Version 2 (IKEv2) packets. An attacker could exploit this vulnerability by sending specifically malformed IKEv2 packets to an affected device. A successful exploit could allow the attacker to cause the ipsecmgr process to restart, which would disrupt ongoing IKE negotiations and result in a temporary DoS condition.Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

The SIP Proxy (SIPD) service in Cisco Unified Presence before 6.0(3) allows remote attackers to cause a denial of service (core dump and service interruption) via a TCP port scan, aka Bug ID CSCsj64533.

Cisco Unified IP Phone 7940, 7940G, 7960, and 7960G running SCCP firmware allows remote attackers to cause a denial of service (reboot) via a long ICMP echo request (ping) packet.