Cisco Unified Personal Communicator 7.0 (1.13056) does not free allocated memory for received data and does not perform validation if memory allocation is successful, causing a remote denial of service condition.

Cisco IOS XR 3.4.0 through 3.9.1, when BGP is enabled, does not properly handle unrecognized transitive attributes, which allows remote attackers to cause a denial of service (peering reset) via a crafted prefix announcement, as demonstrated in the wild in August 2010 with attribute type code 99, aka Bug ID CSCti62211.

Buffer overflows in Cisco Virtual Private Network (VPN) Client 3.5.4 and earlier allows remote attackers to cause a denial of service via (1) an Internet Key Exchange (IKE) with a large Security Parameter Index (SPI) payload, or (2) an IKE packet with a large number of valid payloads.

Memory leak in the Call Telephony Integration (CTI) Framework authentication for Cisco CallManager 3.0 and 3.1 before 3.1(3) allows remote attackers to cause a denial of service (crash and reload) via a series of authentication failures, e.g. via incorrect passwords.

Cisco DSL CPE devices running CBOS 2.4.4 and earlier allows remote attackers to cause a denial of service (hang or memory consumption) via (1) a large packet to the DHCP port, (2) a large packet to the Telnet port, or (3) a flood of large packets to the CPE, which causes the TCP/IP stack to consume large amounts of memory.

Cisco ONS15454 optical transport platform running ONS 3.1.0 to 3.2.0 allows remote attackers to cause a denial of service (reset) by sending IP packets with non-zero Type of Service (TOS) bits to the Timing Control Card (TCC) LAN interface.

Cisco Aironet before 11.21 with Telnet enabled allows remote attackers to cause a denial of service (reboot) via a series of login attempts with invalid usernames and passwords.

Cisco IP Phone (VoIP) models 7910, 7940, and 7960 allow remote attackers to cause a denial of service (crash) via malformed packets as demonstrated by (1) "jolt", (2) "jolt2", (3) "raped", (4) "hping2", (5) "bloop", (6) "bubonic", (7) "mutant", (8) "trash", and (9) "trash2."

Cisco IOS 12.2 and earlier running Cisco Discovery Protocol (CDP) allows remote attackers to cause a denial of service (memory consumption) via a flood of CDP neighbor announcements.

Multiple Cisco networking products allow remote attackers to cause a denial of service on the local network via a series of ARP packets sent to the router's interface that contains a different MAC address for the router, which eventually causes the router to overwrite the MAC address in its ARP table.

Cisco devices IOS 12.0 and earlier allow a remote attacker to cause a crash, or bad route updates, via malformed BGP updates with unrecognized transitive attribute.

Cisco 600 series routers running CBOS 2.0.1 through 2.4.2ap allows remote attackers to cause a denial of service via multiple connections to the router on the (1) HTTP or (2) telnet service, which causes the router to become unresponsive and stop forwarding packets.

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.

Cisco CBOS 2.3.8 and earlier allows remote attackers to cause a denial of service via an ICMP ECHO REQUEST (ping) with the IP Record Route option set.

Web-based configuration utility in Cisco 600 series routers running CBOS 2.0.1 through 2.4.2ap binds itself to port 80 even when web-based configuration services are disabled, which could leave the router open to attack.

Cisco CBOS 2.3.8 and earlier allows remote attackers to cause a denial of service via a series of large ICMP ECHO REPLY (ping) packets, which cause it to enter ROMMON mode and stop forwarding packets.

Cisco IOS 12.1(2)T, 12.1(3)T allow remote attackers to cause a denial of service (reload) via a connection to TCP ports 3100-3999, 5100-5999, 7100-7999 and 10100-10999.

Cisco 12000 with IOS 12.0 and line cards based on Engine 2 and earlier allows remote attackers to cause a denial of service (CPU consumption) by flooding the router with traffic that generates a large number of ICMP Unreachable replies.

PPTP implementation in Cisco IOS 12.1 and 12.2 allows remote attackers to cause a denial of service (crash) via a malformed packet.

Cisco 12000 with IOS 12.0 and line cards based on Engine 2 does not handle the "fragment" keyword in a compiled ACL (Turbo ACL) for packets that are sent to the router, which allows remote attackers to cause a denial of service via a flood of fragments.

Cisco TFTP Server 1.1 allows remote attackers to cause a denial of service (daemon crash) via a crafted (1) read (aka RRQ) or (2) write (aka WRQ) request, or other TFTP packet. NOTE: some of these details are obtained from third party information.

Cisco VPN 3000 series concentrators before 2.5.2(F) allow remote attackers to cause a denial of service via an IP packet with an invalid IP option.

The HTTP server in Cisco IOS 12.0 through 12.1 allows local users to cause a denial of service (crash and reload) via a URL containing a "?/" string.

Cisco 600 routers running CBOS 2.4.1 and earlier allow remote attackers to cause a denial of service via a large ICMP echo (ping) packet.

Unspecified vulnerability in Cisco ASA 5500 Series Adaptive Security Appliance 7.0 before 7.0(8.10), 7.2 before 7.2(4.45), 8.0 before 8.0(5.1), 8.1 before 8.1(2.37), and 8.2 before 8.2(1.15); and Cisco PIX 500 Series Security Appliance; allows remote attackers to cause a denial of service (active IPsec tunnel loss and prevention of new tunnels) via a malformed IKE message through an existing tunnel to UDP port 4500, aka Bug ID CSCtc47782.

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.

Cisco Adaptive Security Appliances (ASA) 5500 series devices with software before 8.2(3) allow remote attackers to cause a denial of service (ASDM syslog outage) via a long URL, aka Bug IDs CSCsm11264 and CSCtb92911.

Buffer overflow in Cisco TACACS+ tac_plus server allows remote attackers to cause a denial of service via a malformed packet with a long length field.

Memory leak in the gk_circuit_info_do_in_acf function in the H.323 implementation in Cisco IOS before 15.0(1)XA allows remote attackers to cause a denial of service (memory consumption) via a large number of calls over a long duration, as demonstrated by InterZone Clear Token (IZCT) test traffic, aka Bug ID CSCsz72535.

Cisco IOS 11.x and 12.x allows remote attackers to cause a denial of service by sending the ENVIRON option to the Telnet daemon before it is ready to accept it, which causes the system to reboot.

Denial of service in Cisco routers running NAT via a PORT command from an FTP client to a Telnet port.

Vulnerability in Cisco 7xx series routers allows a remote attacker to cause a system reload via a TCP connection to the router's TELNET port.

Cisco Catalyst LAN switches running Catalyst 5000 supervisor software allows remote attackers to perform a denial of service by forcing the supervisor module to reload.

Denial of service in Cisco IOS web server allows attackers to reboot the router using a long URL.

Buffer overflow in Cisco 7xx routers through the telnet service.

Attackers can crash a Cisco IOS router or device, provided they can get to an interactive prompt (such as a login). This applies to some IOS 9.x, 10.x, and 11.x releases.

Cisco IOS 12.0 and other versions can be crashed by malicious UDP packets to the syslog port.

A vulnerability in the HTTPS decryption feature of Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition. The vulnerability is due to insufficient validation of Secure Sockets Layer (SSL) server certificates. An attacker could exploit this vulnerability by installing a malformed certificate in a web server and sending a request to it through the Cisco WSA. A successful exploit could allow the attacker to cause an unexpected restart of the proxy process on an affected device.

A vulnerability in the H.264 decoder function of Cisco Meeting Server could allow an unauthenticated, remote attacker to cause a Cisco Meeting Server media process to restart unexpectedly when it receives an illegal H.264 frame. The vulnerability is triggered by an H.264 frame that has an invalid picture parameter set (PPS) value. An attacker could exploit this vulnerability by sending a malformed H.264 frame to the targeted device. An exploit could allow the attacker to cause a denial of service (DoS) condition because the media process could restart. The media session should be re-established within a few seconds, during which there could be a brief interruption in service. Cisco Bug IDs: CSCvg12559.

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 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 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 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.

A vulnerability in the Internet Key Exchange Version 2 (IKEv2) module of Cisco IOS 15.0 through 15.6 and Cisco IOS XE 3.5 through 16.5 could allow an unauthenticated, remote attacker to cause high CPU utilization, traceback messages, or a reload of an affected device that leads to a denial of service (DoS) condition. The vulnerability is due to how an affected device processes certain IKEv2 packets. An attacker could exploit this vulnerability by sending specific IKEv2 packets to an affected device to be processed. A successful exploit could allow the attacker to cause high CPU utilization, traceback messages, or a reload of the affected device that leads to a DoS condition. This vulnerability affects Cisco devices that have the Internet Security Association and Key Management Protocol (ISAKMP) enabled. Although only IKEv2 packets can be used to trigger this vulnerability, devices that are running Cisco IOS Software or Cisco IOS XE Software are vulnerable when ISAKMP is enabled. A device does not need to be configured with any IKEv2-specific features to be vulnerable. Many features use IKEv2, including different types of VPNs such as the following: LAN-to-LAN VPN; Remote-access VPN, excluding SSL VPN; Dynamic Multipoint VPN (DMVPN); and FlexVPN. Cisco Bug IDs: CSCvc41277.

A vulnerability in the HTTP web interface for Cisco Wide Area Application Services (WAAS) could allow an unauthenticated, remote attacker to cause an HTTP Application Optimization (AO) related process to restart, causing a partial denial of service (DoS) condition. The vulnerability is due to lack of input validation of user-supplied input parameters within an HTTP request. An attacker could exploit this vulnerability by sending a crafted HTTP request through the targeted device. An exploit could allow the attacker to cause a DoS condition due to a process unexpectedly restarting. The WAAS could drop traffic during the brief time the process is restarting. Cisco Bug IDs: CSCvc63048.

A vulnerability in SSL traffic decryption for Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause depletion of system memory, aka a Firepower Detection Engine SSL Decryption Memory Consumption Denial of Service vulnerability. If this memory leak persists over time, a denial of service (DoS) condition could develop because traffic can cease to be forwarded through the device. The vulnerability is due to an error in how the Firepower Detection Snort Engine handles SSL traffic decryption and notifications to and from the Adaptive Security Appliance (ASA) handler. An attacker could exploit this vulnerability by sending a steady stream of malicious Secure Sockets Layer (SSL) traffic through the device. An exploit could allow the attacker to cause a DoS condition when the device runs low on system memory. This vulnerability affects Cisco Firepower Threat Defense (FTD) Software Releases 6.0.1 and later, running on any of the following Cisco products: Adaptive Security Appliance (ASA) 5500-X Series Next-Generation Firewalls, Firepower 2100 Series Security Appliances, Firepower 4100 Series Security Appliances, Firepower 9300 Series Security Appliances. Cisco Bug IDs: CSCve02069.

A vulnerability in the TLS cryptography functionality of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reload unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to improper data validation during the TLS 1.3 handshake. An attacker could exploit this vulnerability by sending a crafted TLS 1.3 packet to an affected system through a TLS 1.3-enabled listening socket. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. Note: This vulnerability can also impact the integrity of a device by causing VPN HostScan communication failures or file transfer failures when Cisco ASA Software is upgraded using Cisco Adaptive Security Device Manager (ASDM).

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 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 in the AnyConnect service on an affected device. This vulnerability is due to insufficient resource management when establishing TLS/SSL sessions. An attacker could exploit this vulnerability by sending a series of crafted TLS/SSL messages to the VPN server of an affected device. A successful exploit could allow the attacker to cause the Cisco AnyConnect VPN server to stop accepting new connections, preventing new SSL VPN connections from being established. Existing SSL VPN sessions are not impacted. Note: When the attack traffic stops, the Cisco AnyConnect VPN server recovers gracefully without requiring manual intervention.

A vulnerability in the HTTP Server feature of Cisco IOS XE Software when the Telephony Service feature is enabled could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to a null pointer dereference when accessing specific URLs. An attacker could exploit this vulnerability by sending crafted HTTP traffic to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, causing a DoS condition on the affected device.