CBOS 2.4.1 and earlier in Cisco 600 routers allows remote attackers to cause a denial of service via a slow stream of TCP SYN packets.

The lock manager in Cisco CNS Network Registrar 6.0 through 6.1.1.3 allows remote attackers to cause a denial of service (process crash) via a certain "unexpected packet sequence."

The Fibre Channel over IP (FCIP) implementation in Cisco MDS NX-OS 4.2 and 5.2 on MDS 9000 series switches allows remote attackers to cause a denial of service (module reload) via a crafted FCIP header, aka Bug ID CSCtn93151.

Cisco VPN 3000 Concentrator 2.2.x, and 3.x before 3.5.3, allows remote attackers to cause a denial of service (crash) via a long (1) username or (2) password to the HTML login interface.

Cisco IOS 2.2(18)EW, 12.2(18)EWA, 12.2(14)SZ, 12.2(18)S, 12.2(18)SE, 12.2(18)SV, 12.2(18)SW, and other versions without the "no service dhcp" command, keep undeliverable DHCP packets in the queue instead of dropping them, which allows remote attackers to cause a denial of service (dropped traffic) via multiple undeliverable DHCP packets that exceed the input queue size.

Multiple vulnerabilities in the Control and Provisioning of Wireless Access Points (CAPWAP) protocol processing of Cisco IOS XE Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. These vulnerabilities are due to insufficient validation of CAPWAP packets. An attacker could exploit the vulnerabilities by sending a malformed CAPWAP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to crash and reload, resulting in a DoS condition.

A vulnerability in the proxy service of Cisco AsyncOS for Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to exhaust system memory and cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper memory management in the proxy service of an affected device. An attacker could exploit this vulnerability by establishing a large number of HTTPS connections to the affected device. A successful exploit could allow the attacker to cause the system to stop processing new connections, which could result in a DoS condition. Note: Manual intervention may be required to recover from this situation.

Multiple vulnerabilities in the Control and Provisioning of Wireless Access Points (CAPWAP) protocol processing of Cisco IOS XE Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. These vulnerabilities are due to insufficient validation of CAPWAP packets. An attacker could exploit the vulnerabilities by sending a malformed CAPWAP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to crash and reload, resulting in a DoS condition.

A vulnerability in the email scanning algorithm of Cisco AsyncOS software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to perform a denial of service (DoS) attack against an affected device. This vulnerability is due to insufficient input validation of incoming emails. An attacker could exploit this vulnerability by sending a crafted email through Cisco ESA. A successful exploit could allow the attacker to exhaust all the available CPU resources on an affected device for an extended period of time, preventing other emails from being processed and resulting in a DoS condition.

A vulnerability in the web-based management interface of Cisco Integrated Management Controller (IMC) Software could allow an unauthenticated, remote attacker to cause the web-based management interface to unexpectedly restart. The vulnerability is due to insufficient input validation on the web-based management interface. An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected device. A successful exploit could allow the attacker to cause the interface to restart, resulting in a denial of service (DoS) condition.

A vulnerability in the TCP Normalizer of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software operating in transparent mode could allow an unauthenticated, remote attacker to poison MAC address tables, resulting in a denial of service (DoS) vulnerability. This vulnerability is due to incorrect handling of certain TCP segments when the affected device is operating in transparent mode. An attacker could exploit this vulnerability by sending a crafted TCP segment through an affected device. A successful exploit could allow the attacker to poison the MAC address tables in adjacent devices, resulting in network disruption.

Cisco routers and switches running IOS 12.0 through 12.2.1 allows a remote attacker to cause a denial of service via a flood of UDP packets.

IP Security VPN Services Module (VPNSM) in Cisco Catalyst 6500 Series Switch and the Cisco 7600 Series Internet Routers running IOS before 12.2(17b)SXA, before 12.2(17d)SXB, or before 12.2(14)SY03 could allow remote attackers to cause a denial of service (device crash and reload) via a malformed Internet Key Exchange (IKE) packet.

Cisco CatOS 5.x before 5.5(20) through 8.x before 8.2(2) and 8.3(2)GLX, as used in Catalyst switches, allows remote attackers to cause a denial of service (system crash and reload) by sending invalid packets instead of the final ACK portion of the three-way handshake to the (1) Telnet, (2) HTTP, or (3) SSH services, aka "TCP-ACK DoS attack."

A vulnerability in the Protection Against Distributed Denial of Service Attacks feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to conduct denial of service (DoS) attacks to or through the affected device. This vulnerability is due to incorrect programming of the half-opened connections limit, TCP SYN flood limit, or TCP SYN cookie features when the features are configured in vulnerable releases of Cisco IOS XE Software. An attacker could exploit this vulnerability by attempting to flood traffic to or through the affected device. A successful exploit could allow the attacker to initiate a DoS attack to or through an affected device.

The Fabric Interconnect component in Cisco Unified Computing System (UCS) 2.0 allows remote attackers to cause a denial of service (process crash) via an attempted SSH session, aka Bug ID CSCtt94543.

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 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 NULL pointer dereference, resulting in a crash of the dhcpd process. While the dhcpd process is restarting, which may take up to 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. Note: Only the dhcpd process crashes and eventually restarts automatically. The router does not reload.

Cisco Internetwork Operating System (IOS) 12.0S through 12.3T attempts to process SNMP solicited operations on improper ports (UDP 162 and a randomly chosen UDP port), which allows remote attackers to cause a denial of service (device reload and memory corruption).

A vulnerability in the software-based SSL/TLS message handler of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. This vulnerability is due to insufficient validation of SSL/TLS messages when the device performs software-based SSL/TLS decryption. An attacker could exploit this vulnerability by sending a crafted SSL/TLS message to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Note: Datagram TLS (DTLS) messages cannot be used to exploit this vulnerability.

A vulnerability in the processing of SSH connections for multi-instance deployments of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on the affected device. This vulnerability is due to a lack of proper error handling when an SSH session fails to be established. An attacker could exploit this vulnerability by sending a high rate of crafted SSH connections to the instance. A successful exploit could allow the attacker to cause resource exhaustion, which causes a DoS condition on the affected device. The device must be manually reloaded to recover.

A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to trigger a denial of service (DoS) condition. This vulnerability is due to improper input validation when parsing HTTPS requests. An attacker could exploit this vulnerability by sending a malicious HTTPS request to an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

The do_change_cipher_spec function in OpenSSL 0.9.6c to 0.9.6k, and 0.9.7a to 0.9.7c, allows remote attackers to cause a denial of service (crash) via a crafted SSL/TLS handshake that triggers a null dereference.

A vulnerability in the memory management of Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper resource management when connection rates are high. An attacker could exploit this vulnerability by opening a significant number of connections on an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition.

Memory leak in Cisco IOS before 15.1(1)SY, when IKEv2 debugging is enabled, allows remote attackers to cause a denial of service (memory consumption) via crafted packets, aka Bug ID CSCtn22376.

A vulnerability in Cisco WebEx Meetings Server could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to insufficient limitations on the number of connections that can be made to the affected software. An attacker could exploit this vulnerability by opening multiple connections to the server and exhausting server resources. A successful exploit could cause the server to reload, resulting in a DoS condition. Cisco Bug IDs: CSCvf41006.

A vulnerability in the detection engine parsing of IPv6 packets for Cisco Firepower System Software could allow an unauthenticated, remote attacker to cause high CPU utilization or to cause a denial of service (DoS) condition because the Snort process restarts unexpectedly. The vulnerability is due to improper input validation of the fields in the IPv6 extension header packet. An attacker could exploit this vulnerability by sending a malicious IPv6 packet to the detection engine on the targeted device. An exploit could allow the attacker to cause a DoS condition if the Snort process restarts and traffic inspection is bypassed or traffic is dropped. This vulnerability is specific to IPv6 traffic only. This vulnerability affects Cisco Firepower System Software Releases 6.0 and later when the software has one or more file action policies configured and is running on any of the following Cisco products: 3000 Series Industrial Security Appliances (ISR), Adaptive Security Appliance (ASA) 5500-X Series with FirePOWER Services, Adaptive Security Appliance (ASA) 5500-X Series Next-Generation Firewalls, Advanced Malware Protection (AMP) for Networks, 7000 Series Appliances, Advanced Malware Protection (AMP) for Networks, 8000 Series Appliances, FirePOWER 7000 Series Appliances, FirePOWER 8000 Series Appliances, Firepower Threat Defense for Integrated Services Routers (ISRs), Firepower 2100 Series Security Appliances, Firepower 4100 Series Security Appliances, Firepower 9300 Series Security Appliances, Virtual Next-Generation Intrusion Prevention System (NGIPSv) for VMware. Cisco Bug IDs: CSCvd34776.

A vulnerability in the General Packet Radio Service (GPRS) Tunneling Protocol ingress packet handler of Cisco ASR 5500 System Architecture Evolution (SAE) Gateways could allow an unauthenticated, remote attacker to cause a partial denial of service (DoS) condition on an affected device. The vulnerability is due to improper input validation of GPRS Tunneling Protocol packet headers. An attacker could exploit this vulnerability by sending a malformed GPRS Tunneling Protocol packet to an affected device. A successful exploit could allow the attacker to cause the GTPUMGR process on an affected device to restart unexpectedly, resulting in a partial DoS condition. If the GTPUMGR process restarts, there could be a brief impact on traffic passing through the device. Cisco Bug IDs: CSCve07119.

A vulnerability in Session Initiation Protocol (SIP) call handling in Cisco IP Phone 8800 Series devices could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition because the SIP process unexpectedly restarts. All active phone calls are dropped as the SIP process restarts. The vulnerability is due to incomplete input validation of the SIP packet header. An attacker could exploit this vulnerability by sending a malformed SIP packet to a targeted phone. An exploit could allow the attacker to cause a DoS condition because all phone calls are dropped when the SIP process unexpectedly restarts. Cisco Bug IDs: CSCvc62590.

A vulnerability in the Independent Computing Architecture (ICA) accelerator feature for the Cisco Wide Area Application Services (WAAS) could allow an unauthenticated, remote attacker to cause an ICA application optimization-related process to restart, resulting in a partial denial of service (DoS) condition. The vulnerability is due to improperly aborting a connection when an unexpected protocol packet is received. An attacker could exploit this vulnerability by sending a crafted ICA traffic through the targeted device. A successful exploit could allow the attacker to cause a DoS condition that is due to a process unexpectedly restarting. The Cisco WAAS could drop ICA traffic while the process is restarting. This vulnerability affects Cisco Wide Area Application Services (WAAS) and Cisco Virtual Wide Area Application Services (vWAAS). Cisco Bug IDs: CSCve74457.

A vulnerability in the implementation of Session Initiation Protocol (SIP) functionality in Cisco Small Business SPA51x Series IP Phones could allow an unauthenticated, remote attacker to cause an affected device to become unresponsive, resulting in a denial of service (DoS) condition. The vulnerability is due to the improper handling of SIP request messages by an affected device. An attacker could exploit this vulnerability by sending malformed SIP messages to an affected device. A successful exploit could allow the attacker to cause the affected device to become unresponsive, resulting in a DoS condition that persists until the device is restarted manually. This vulnerability affects Cisco Small Business SPA51x Series IP Phones that are running Cisco SPA51x Firmware Release 7.6.2SR1 or earlier. Cisco Bug IDs: CSCvc63982.

A vulnerability in the gRPC code of Cisco IOS XR Software for Cisco Network Convergence System (NCS) 5500 Series Routers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition when the emsd service stops. The vulnerability is due to the software's inability to process HTTP/2 packets. An attacker could exploit this vulnerability by sending a malformed HTTP/2 frame to the affected device. A successful exploit could allow the attacker to create a DoS condition when the emsd service stops. Cisco Bug IDs: CSCvb99388.

The sccp-protocol component in Cisco IP Communicator (CIPC) 7.0 through 8.6 does not limit the rate of SCCP messages to Cisco Unified Communications Manager (CUCM), which allows remote attackers to cause a denial of service via vectors that trigger (1) on hook and (2) off hook messages, as demonstrated by a Plantronics headset, aka Bug ID CSCti40315.

Cisco 11000 Series Content Services Switches (CSS) running WebNS 5.0(x) before 05.0(04.07)S, and 6.10(x) before 06.10(02.05)S allow remote attackers to cause a denial of service (device reset) via a malformed packet to UDP port 5002.

A vulnerability in the implementation of Session Initiation Protocol (SIP) functionality in Cisco Small Business SPA50x, SPA51x, and SPA52x Series IP Phones could allow an unauthenticated, remote attacker to cause an affected device to become unresponsive, resulting in a denial of service (DoS) condition. The vulnerability is due to the improper handling of SIP request messages by an affected device. An attacker could exploit this vulnerability by using formatted specifiers in a SIP payload that is sent to an affected device. A successful exploit could allow the attacker to cause the affected device to become unresponsive, resulting in a DoS condition that persists until the device is restarted manually. This vulnerability affects Cisco Small Business SPA50x, SPA51x, and SPA52x Series IP Phones that are running firmware release 7.6.2SR1 or earlier. Cisco Bug IDs: CSCvc63986.

A vulnerability in the ingress packet processing function of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper resource allocation when an affected device processes network traffic in software switching mode (punted). An attacker could exploit this vulnerability by sending specific streams of Layer 2 or Layer 3 protocol data units (PDUs) to an affected device. A successful exploit could cause the affected device to run out of buffer resources, which could make the device unable to process or forward traffic, resulting in a DoS condition. The device would need to be restarted to regain functionality.

The voice-sipstack component in Cisco Unified Communications Manager (CUCM) 8.5 allows remote attackers to cause a denial of service (core dump) via vectors involving SIP messages that arrive after an upgrade, aka Bug ID CSCtj87367.

A vulnerability in the Trust Verification Service (TVS) of Cisco Unified Communications Manager could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper handling of Transport Layer Security (TLS) traffic by the affected software. An attacker could exploit this vulnerability by generating incomplete traffic streams. A successful exploit could allow the attacker to deny access to the TVS for an affected device, resulting in a DoS condition, until an administrator restarts the service. Known Affected Releases 10.0(1.10000.24) 10.5(2.10000.5) 11.0(1.10000.10) 9.1(2.10000.28). Cisco Bug IDs: CSCux21905.

Cisco Sourcefire Snort 3.0 before build 233 mishandles Ether Type Validation. Since valid ether type and IP protocol numbers do not overlap, Snort++ stores all protocol decoders in a single array. That makes it possible to craft packets that have IP protocol numbers in the ether type field which will confuse the Snort++ decoder. For example, an eth:llc:snap:icmp6 packet will cause a crash because there is no ip6 header with which to calculate the icmp6 checksum. Affected decoders include gre, llc, trans_bridge, ciscometadata, linux_sll, and token_ring. The fix adds a check in the packet manager to validate the ether type before indexing the decoder array. An out of range ether type will raise 116:473.

The XML API service in the Fabric Interconnect component in Cisco Unified Computing System (UCS) allows remote attackers to cause a denial of service (API service outage) via a malformed XML document in a packet, aka Bug ID CSCtg48206.

OpenSSL 0.9.6 before 0.9.6d does not properly handle unknown message types, which allows remote attackers to cause a denial of service (infinite loop), as demonstrated using the Codenomicon TLS Test Tool.

The sensor in Cisco Intrusion Prevention System (IPS) 7.0 and 7.1 allows remote attackers to cause a denial of service (file-handle exhaustion and mainApp hang) by making authentication attempts that exceed the configured limit, aka Bug ID CSCto51204.

Cisco Unified Contact Center Express (aka CCX) 8.0 and 8.5 allows remote attackers to cause a denial of service via network traffic, as demonstrated by an SEC-BE-STABLE test case, aka Bug ID CSCth33834.

The cat6000-dot1x component in Cisco IOS 12.2 before 12.2(33)SXI7 does not properly handle (1) a loop between a dot1x enabled port and an open-authentication dot1x enabled port and (2) a loop between a dot1x enabled port and a non-dot1x port, which allows remote attackers to cause a denial of service (traffic storm) via unspecified vectors that trigger many Spanning Tree Protocol (STP) Bridge Protocol Data Unit (BPDU) frames, aka Bug ID CSCtq36327.

A vulnerability in the ICMP ingress packet processing of Cisco TelePresence Collaboration Endpoint (CE) Software could allow an unauthenticated, remote attacker to cause the TelePresence endpoint to reload unexpectedly, resulting in a denial of service (DoS) condition. The vulnerability is due to incomplete input validation for the size of a received ICMP packet. An attacker could exploit this vulnerability by sending a crafted ICMP packet to the local IP address of the targeted endpoint. A successful exploit could allow the attacker to cause a DoS of the TelePresence endpoint, during which time calls could be dropped. This vulnerability would affect either IPv4 or IPv6 ICMP traffic. This vulnerability affects the following Cisco TelePresence products when running software release CE8.1.1, CE8.2.0, CE8.2.1, CE8.2.2, CE 8.3.0, or CE8.3.1: Spark Room OS, TelePresence DX Series, TelePresence MX Series, TelePresence SX Quick Set Series, TelePresence SX Series. Cisco Bug IDs: CSCvb95396.

Cisco ONS 15327 before 4.1(3), ONS 15454 before 4.6(1), and ONS 15454 SD before 4.1(3) allows remote attackers to cause a denial of service (reset) by not sending the ACK portion of the TCP three-way handshake and sending an invalid response instead.

The DNS server for Cisco Content Service Switch (CSS) 11000 and 11500, when prompted for a nonexistent AAAA record, responds with response code 3 (NXDOMAIN or "Name Error") instead of response code 0 ("No Error"), which allows remote attackers to cause a denial of service (inaccessible domain) by forcing other DNS servers to send and cache a request for a AAAA record to the vulnerable server.

Cisco VPN 3000 series concentrators and Cisco VPN 3002 Hardware Client 2.x.x through 3.6.7 allows remote attackers to cause a denial of service (reload) via a malformed SSH initialization packet.