A vulnerability in the boot process of Cisco IOS XR Software could allow an authenticated, local attacker to bypass Cisco IOS XR image signature verification and load unverified software on an affected device. To exploit this vulnerability, the attacker must have root-system privileges on the affected device. This vulnerability is due to incomplete validation of files in the boot verification process. An attacker could exploit this vulnerability by manipulating the system configuration options to bypass some of the integrity checks that are performed during the boot process. A successful exploit could allow the attacker to control the boot configuration, which could enable them to bypass the requirement to run Cisco-signed images or alter the security properties of the running system. Note: Because exploitation of this vulnerability could result in the attacker bypassing Cisco image verification, Cisco has raised the Security Impact Rating (SIR) of this advisory from Medium to High.

A vulnerability in the boot process of Cisco IOS XR Software could allow an authenticated, local attacker with high privileges to bypass the Secure Boot functionality and load unverified software on an affected device. To exploit this vulnerability, the attacker must have root-system privileges on the affected device. This vulnerability is due to insufficient verification of modules in the software load process. An attacker could exploit this vulnerability by manipulating the loaded binaries to bypass some of the integrity checks that are performed during the booting process. A successful exploit could allow the attacker to control the boot configuration, which could enable them to bypass the requirement to run Cisco-signed images or alter the security properties of the running system. Note: This vulnerability affects Cisco IOS XR Software, not the Secure Boot feature. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability.

Cisco IOS XR software health check opens TCP port 6379 by default on activation. An attacker can connect to the Redis instance on the open port and allow access to the Redis instance that is running within the NOSi container.

A vulnerability in the IPsec packet processor of Cisco IOS XR Software could allow an unauthenticated remote attacker to cause a denial of service (DoS) condition for IPsec sessions to an affected device. The vulnerability is due to improper handling of packets by the IPsec packet processor. An attacker could exploit this vulnerability by sending malicious ICMP error messages to an affected device that get punted to the IPsec packet processor. A successful exploit could allow the attacker to deplete IPsec memory, resulting in all future IPsec packets to an affected device being dropped by the device. Manual intervention is required to recover from this situation.

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).

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 forwarding component of Cisco IOS XR Software for Cisco Network Convergence System (NCS) 5500 Series Routers could allow an authenticated, local attacker to cause the router to stop forwarding data traffic across Traffic Engineering (TE) tunnels, resulting in a denial of service (DoS) condition. More Information: CSCvd16665. Known Affected Releases: 6.2.11.BASE. Known Fixed Releases: 6.1.3 6.1.2 6.3.1.8i.BASE 6.2.11.8i.BASE 6.2.2.9i.BASE 6.1.32.11i.BASE 6.1.31.10i.BASE 6.1.4.3i.BASE.

A vulnerability in Google-defined remote procedure call (gRPC) handling in Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause the Event Management Service daemon (emsd) to crash due to a system memory leak, resulting in a denial of service (DoS) condition. This vulnerability affects Cisco IOS XR Software with gRPC enabled. More Information: CSCvb14433. Known Affected Releases: 6.1.1.BASE 6.2.1.BASE. Known Fixed Releases: 6.2.1.22i.MGBL 6.1.22.9i.MGBL 6.1.21.12i.MGBL 6.1.2.13i.MGBL.

Cisco ASR 9000 devices with software 5.3.0.BASE do not recognize that certain ACL entries have a single-host constraint, which allows remote attackers to bypass intended network-resource access restrictions by using an address that was not supposed to have been allowed, aka Bug ID CSCur28806.

The DHCPv4 server in Cisco IOS XR 5.2.2 on ASR 9000 devices allows remote attackers to cause a denial of service (service outage) via a flood of crafted DHCP packets, aka Bug ID CSCup67822.

Cisco IOS XR allows remote attackers to cause a denial of service (RSVP process reload) via a malformed RSVP packet, aka Bug ID CSCur69192.

The SNMPv2 implementation in Cisco IOS XR allows remote authenticated users to cause a denial of service (snmpd daemon reload) via a malformed SNMP packet, aka Bug ID CSCur25858.

The DHCPv6 implementation in Cisco IOS XR allows remote attackers to cause a denial of service (device crash) via a malformed packet, aka Bug IDs CSCum85558, CSCum20949, CSCul61849, and CSCul71149.

The DHCPv6 implementation in Cisco IOS XR allows remote attackers to cause a denial of service (process hang) via a malformed packet, aka Bug ID CSCul80924.

Cisco IOS XR does not properly throttle ICMPv6 redirect packets, which allows remote attackers to cause a denial of service (IPv4 and IPv6 transit outage) via crafted redirect messages, aka Bug ID CSCum14266.

The SNMP module in Cisco IOS XR allows remote attackers to cause a denial of service (process reload) via a request for an unspecified MIB, aka Bug ID CSCuh43144.

The RIP process in Cisco IOS XR allows remote attackers to cause a denial of service (process crash) via a crafted version-2 RIP packet, aka Bug ID CSCue46731.

Cisco IOS XR allows local users to cause a denial of service (Silicon Packet Processor memory corruption, improper mutex handling, and device reload) by starting an outbound flood of large ICMP Echo Request packets and stopping this with a CTRL-C sequence, aka Bug ID CSCui60347.

Memory leak in the SNMP module in Cisco IOS XR allows remote authenticated users to cause a denial of service (memory consumption and process restart) via crafted SNMP packets, aka Bug ID CSCue31546.

Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an invalid attribute, as demonstrated in the wild on 17 August 2009.

The (1) Airline Product Set (aka ALPS), (2) Serial Tunnel Code (aka STUN), (3) Block Serial Tunnel Code (aka BSTUN), (4) Native Client Interface Architecture (NCIA) support, (5) Data-link switching (aka DLSw), (6) Remote Source-Route Bridging (RSRB), (7) Point to Point Tunneling Protocol (PPTP), (8) X.25 for Record Boundary Preservation (RBP), (9) X.25 over TCP (XOT), and (10) X.25 Routing features in Cisco IOS 12.2 and 12.4 allows remote attackers to cause a denial of service (device reload) via a series of crafted TCP packets.

Unspecified vulnerability in Cisco IOS 12.0 through 12.4 allows context-dependent attackers to cause a denial of service (device restart and BGP routing table rebuild) via certain regular expressions in a "show ip bgp regexp" command. NOTE: unauthenticated remote attacks are possible in environments with anonymous telnet and Looking Glass access.

Cisco IOS XR, when configured for Multi Protocol Label Switching (MPLS) and running on Cisco CRS-1 routers, allows remote attackers to cause a denial of service (Modular Services Cards (MSC) crash or "MPLS packet handling problems") via certain MPLS packets, as identified by Cisco bug IDs (1) CSCsd15970 and (2) CSCsd55531.

Cisco IOS XR, when configured for Multi Protocol Label Switching (MPLS) and running on Cisco CRS-1 or Cisco 12000 series routers, allows remote attackers to cause a denial of service (Line card crash) via certain MPLS packets, as identified by Cisco bug ID CSCsc77475.