Multiple vulnerabilities in the Distance Vector Multicast Routing Protocol (DVMRP) feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to either immediately crash the Internet Group Management Protocol (IGMP) process or make it consume available memory and eventually crash. The memory consumption may negatively impact other processes that are running on the device. These vulnerabilities are due to the incorrect handling of IGMP packets. An attacker could exploit these vulnerabilities by sending crafted IGMP traffic to an affected device. A successful exploit could allow the attacker to immediately crash the IGMP process or cause memory exhaustion, resulting in other processes becoming unstable. These processes may include, but are not limited to, interior and exterior routing protocols. Cisco will release software updates that address these vulnerabilities.

A vulnerability in the Distance Vector Multicast Routing Protocol (DVMRP) feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to exhaust process memory of an affected device. The vulnerability is due to insufficient queue management for Internet Group Management Protocol (IGMP) packets. An attacker could exploit this vulnerability by sending crafted IGMP traffic to an affected device. A successful exploit could allow the attacker to cause memory exhaustion, resulting in instability of other processes. These processes may include, but are not limited to, interior and exterior routing protocols. Cisco will release software updates that address this vulnerability.

A vulnerability in the Cisco Discovery Protocol implementation for Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to execute arbitrary code or cause a reload on an affected device. The vulnerability is due to improper validation of string input from certain fields in Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to cause a stack overflow, which could allow the attacker to execute arbitrary code with administrative privileges on an affected device. Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).

A vulnerability in the Cisco Discovery Protocol implementation for Cisco FXOS Software, Cisco IOS XR Software, and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to a missing check when the affected software processes Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to exhaust system memory, causing the device to reload. Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).

Multiple Buffer Overflow vulnerabilities in the Link Layer Discovery Protocol (LLDP) subsystem of Cisco IOS Software, Cisco IOS XE Software, and Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition or execute arbitrary code with elevated privileges on an affected device. Cisco Bug IDs: CSCuo17183, CSCvd73487.

The DHCP relay subsystem of Cisco IOS 12.2 through 15.6 and Cisco IOS XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code and gain full control of an affected system. The attacker could also cause an affected system to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to a buffer overflow condition in the DHCP relay subsystem of the affected software. An attacker could exploit this vulnerability by sending a crafted DHCP Version 4 (DHCPv4) packet to an affected system. A successful exploit could allow the attacker to execute arbitrary code and gain full control of the affected system or cause the affected system to reload, resulting in a DoS condition. Cisco Bug IDs: CSCsm45390, CSCuw77959.

A vulnerability in the implementation of Network Address Translation (NAT) functionality in Cisco IOS 12.4 through 15.6 could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to the improper translation of H.323 messages that use the Registration, Admission, and Status (RAS) protocol and are sent to an affected device via IPv4 packets. An attacker could exploit this vulnerability by sending a crafted H.323 RAS packet through an affected device. A successful exploit could allow the attacker to cause the affected device to crash and reload, resulting in a DoS condition. This vulnerability affects Cisco devices that are configured to use an application layer gateway with NAT (NAT ALG) for H.323 RAS messages. By default, a NAT ALG is enabled for H.323 RAS messages. Cisco Bug IDs: CSCvc57217.

A vulnerability in the iPXE boot function of Cisco IOS XR software could allow an authenticated, local attacker to install an unverified software image on an affected device. This vulnerability is due to insufficient image verification. An attacker could exploit this vulnerability by manipulating the boot parameters for image verification during the iPXE boot process on an affected device. A successful exploit could allow the attacker to boot an unverified software image on the affected device.

A vulnerability in the PPP over Ethernet (PPPoE) termination feature of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, adjacent attacker to crash the pppma process, resulting in a denial of service (DoS) condition. This vulnerability is due to the improper handling of malformed PPPoE packets that are received on a router that is running Broadband Network Gateway (BNG) functionality with PPPoE termination on a Lightspeed-based or Lightspeed-Plus-based line card. An attacker could exploit this vulnerability by sending a crafted PPPoE packet to an affected line card interface that does not terminate PPPoE. A successful exploit could allow the attacker to crash the pppma process, resulting in a DoS condition for PPPoE traffic across the router.

A vulnerability in the IPv6 subsystem of Cisco IOS XR Software Release 5.3.4 for the Cisco Aggregation Services Router (ASR) 9000 Series could allow an unauthenticated, remote attacker to trigger a reload of one or more Trident-based line cards, resulting in a denial of service (DoS) condition. The vulnerability is due to incorrect handling of IPv6 packets with a fragment header extension. An attacker could exploit this vulnerability by sending IPv6 packets designed to trigger the issue either to or through the Trident-based line card. A successful exploit could allow the attacker to trigger a reload of Trident-based line cards, resulting in a DoS during the period of time the line card takes to restart. This vulnerability affects Cisco Aggregation Services Router (ASR) 9000 Series when the following conditions are met: The router is running Cisco IOS XR Software Release 5.3.4, and the router has installed Trident-based line cards that have IPv6 configured. A software maintenance upgrade (SMU) has been made available that addresses this vulnerability. The fix has also been incorporated into service pack 7 for Cisco IOS XR Software Release 5.3.4. Cisco Bug IDs: CSCvg46800.

A vulnerability in the UDP broadcast forwarding function of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on the affected device. The vulnerability is due to improper handling of UDP broadcast packets that are forwarded to an IPv4 helper address. An attacker could exploit this vulnerability by sending multiple UDP broadcast packets to the affected device. An exploit could allow the attacker to cause a buffer leak on the affected device, eventually resulting in a DoS condition requiring manual intervention to recover. This vulnerability affects all Cisco IOS XR platforms running 6.3.1, 6.2.3, or earlier releases of Cisco IOS XR Software when at least one IPv4 helper address is configured on an interface of the device. Cisco Bug IDs: CSCvi35625.

A vulnerability in the Local Packet Transport Services (LPTS) feature set of Cisco ASR 9000 Series Aggregation Services Router Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to a lack of input and validation checking on certain Precision Time Protocol (PTP) ingress traffic to an affected device. An attacker could exploit this vulnerability by injecting malformed traffic into an affected device. A successful exploit could allow the attacker to cause services on the device to become unresponsive, resulting in a DoS condition. Cisco Bug IDs: CSCvj22858.

A vulnerability in the implementation of Border Gateway Protocol (BGP) 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 certain BGP update messages. An attacker could exploit this vulnerability by sending BGP update messages that include a specific, malformed attribute to be processed by an affected system. A successful exploit could allow the attacker to 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.

A vulnerability in the Multiprotocol Label Switching (MPLS) Operations, Administration, and Maintenance (OAM) implementation of Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, adjacent attacker to trigger a denial of service (DoS) condition on an affected device. The vulnerability is due to the incorrect handling of certain MPLS OAM packets. An attacker could exploit this vulnerability by sending malicious MPLS OAM packets to an affected device. A successful exploit could allow the attacker to cause the lspvserver process to crash. The crash could lead to system instability and the inability to process or forward traffic though the device, resulting in a DoS condition that require manual intervention to restore normal operating conditions.

A vulnerability in the Secure Shell (SSH) authentication function of Cisco IOS XR Software could allow an authenticated, remote attacker to successfully log in to an affected device using two distinct usernames. The vulnerability is due to a logic error that may occur when certain sequences of actions are processed during an SSH login event on the affected device. An attacker could exploit this vulnerability by initiating an SSH session to the device with a specific sequence that presents the two usernames. A successful exploit could result in logging data misrepresentation, user enumeration, or, in certain circumstances, a command authorization bypass. See the Details section for more information.

A vulnerability in the implementation of Border Gateway Protocol (BGP) functionality in Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected system. The vulnerability is due to incorrect processing of certain BGP update messages. An attacker could exploit this vulnerability by sending BGP update messages that include a specific set of attributes to be processed by an affected system. A successful exploit could allow the attacker to cause the BGP process to restart unexpectedly, resulting in a DoS condition. The Cisco implementation of BGP accepts incoming BGP traffic from explicitly defined peers only. 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.

A vulnerability in the TCP flags inspection feature for access control lists (ACLs) on Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to bypass protection offered by a configured ACL on an affected device. The vulnerability is due to incorrect processing of the ACL applied to an interface of an affected device when Cisco Express Forwarding load balancing using the 3-tuple hash algorithm is enabled. An attacker could exploit this vulnerability by sending traffic through an affected device that should otherwise be denied by the configured ACL. An exploit could allow the attacker to bypass protection offered by a configured ACL on the affected device. There are workarounds that address this vulnerability. Affected Cisco IOS XR versions are: Cisco IOS XR Software Release 5.1.1 and later till first fixed. First Fixed Releases: 6.5.2 and later, 6.6.1 and later.

A vulnerability in a CLI command related to the virtualization manager (VMAN) in Cisco IOS XR Software for Cisco ASR 9000 Series Aggregation Services Routers could allow an authenticated, local attacker to execute arbitrary commands on the underlying Linux operating system with root privileges. The vulnerability is due to insufficient validation of arguments passed to a specific VMAN CLI command on an affected device. An attacker who has valid administrator access to an affected device could exploit this vulnerability by including malicious input as the argument of an affected command. A successful exploit could allow the attacker to run arbitrary commands on the underlying operating system with root privileges, which may lead to complete system compromise.

A vulnerability in the implementation of the Border Gateway Protocol (BGP) 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 a specific BGP attribute. An attacker could exploit this vulnerability by sending BGP update messages that include a specific, malformed attribute to be processed by an affected system. A successful exploit could allow the attacker to 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.

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.

Multiple vulnerabilities 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 vulnerabilities are due to incorrect processing of BGP update messages that contain crafted EVPN attributes. An attacker could exploit these vulnerabilities by sending BGP EVPN update messages with malformed attributes to be processed by an affected system. A successful exploit could allow the attacker to 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 these vulnerabilities, 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.

Multiple vulnerabilities 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 vulnerabilities are due to incorrect processing of BGP update messages that contain crafted EVPN attributes. An attacker could exploit these vulnerabilities by sending BGP EVPN update messages with malformed attributes to be processed by an affected system. A successful exploit could allow the attacker to 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 these vulnerabilities, 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.

A vulnerability in the implementation of the Intermediate System–to–Intermediate System (IS–IS) routing protocol functionality in Cisco IOS XR Software could allow an authenticated, remote attacker to cause a denial of service (DoS) condition in the IS–IS process. The vulnerability is due to improper handling of a Simple Network Management Protocol (SNMP) request for specific Object Identifiers (OIDs) by the IS–IS process. An attacker could exploit this vulnerability by sending a crafted SNMP request to the affected device. A successful exploit could allow the attacker to cause a DoS condition in the IS–IS process.

A vulnerability in task group assignment for a specific CLI command in Cisco IOS XR Software could allow an authenticated, local attacker to execute that command, even though administrative privileges should be required. The attacker must have valid credentials on the affected device. The vulnerability is due to incorrect mapping in the source code of task group assignments for a specific command. An attacker could exploit this vulnerability by issuing the command, which they should not be authorized to issue, on an affected device. A successful exploit could allow the attacker to invalidate the integrity of the disk and cause the device to restart. This vulnerability could allow a user with read permissions to issue a specific command that should require Administrator privileges.

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.

A vulnerability in the Layer 2 punt code of Cisco IOS XR Software running on Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, adjacent attacker to cause the affected line card to reboot. This vulnerability is due to incorrect handling of specific Ethernet frames that cause a spin loop that can make the network processors unresponsive. An attacker could exploit this vulnerability by sending specific types of Ethernet frames on the segment where the affected line cards are attached. A successful exploit could allow the attacker to cause the affected line card to reboot.

A vulnerability in the SSH Server process of Cisco IOS XR Software could allow an authenticated, remote attacker to overwrite and read arbitrary files on the local device. This vulnerability is due to insufficient input validation of arguments that are supplied by the user for a specific file transfer method. An attacker with lower-level privileges could exploit this vulnerability by specifying Secure Copy Protocol (SCP) parameters when authenticating to a device. A successful exploit could allow the attacker to elevate their privileges and retrieve and upload files on a device that they should not have access to.

Multiple vulnerabilities in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker with a low-privileged account to elevate privileges on an affected device. For more information about these vulnerabilities, see the Details section of this advisory.

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.

Multiple vulnerabilities in the CLI of Cisco IOS XR Software could allow an authenticated, local attacker to gain access to the underlying root shell of an affected device and execute arbitrary commands with root privileges. For more information about these vulnerabilities, see the Details section of this advisory.