The HTTP/2 protocol allows a denial of service (server resource consumption) because request cancellation can reset many streams quickly, as exploited in the wild in August through October 2023.

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 Connectivity Fault Management (CFM) feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to incorrect processing of invalid continuity check messages (CCMs). An attacker could exploit this vulnerability by sending crafted CCMs to an affected device. A successful exploit could allow the attacker to cause the CFM service to crash when a user displays information about maintenance end points (MEPs) for peer MEPs on an affected device.

A vulnerability in the access control list (ACL) processing on MPLS interfaces in the ingress direction of Cisco IOS XR Software could allow an unauthenticated, remote attacker to bypass a configured ACL. This vulnerability is due to incomplete support for this feature. An attacker could exploit this vulnerability by attempting to send traffic through an affected device. A successful exploit could allow the attacker to bypass an ACL on the affected device. There are workarounds that address this vulnerability. This advisory is part of the September 2023 release of the Cisco IOS XR Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: September 2023 Semiannual Cisco IOS XR Software Security Advisory Bundled Publication .

A vulnerability in Cisco IOS XR Software image verification checks could allow an authenticated, local attacker to execute arbitrary code on the underlying operating system. This vulnerability is due to a time-of-check, time-of-use (TOCTOU) race condition when an install query regarding an ISO image is performed during an install operation that uses an ISO image. An attacker could exploit this vulnerability by modifying an ISO image and then carrying out install requests in parallel. A successful exploit could allow the attacker to execute arbitrary code on an affected device.

A vulnerability in the GRand Unified Bootloader (GRUB) for Cisco IOS XR Software could allow an unauthenticated attacker with physical access to the device to view sensitive files on the console using the GRUB bootloader command line. This vulnerability is due to the inclusion of unnecessary commands within the GRUB environment that allow sensitive files to be viewed. An attacker could exploit this vulnerability by being connected to the console port of the Cisco IOS XR device when the device is power-cycled. A successful exploit could allow the attacker to view sensitive files that could be used to conduct additional attacks against the device.

A vulnerability in the Unidirectional Link Detection (UDLD) feature of Cisco FXOS Software, Cisco IOS Software, Cisco IOS XE Software, Cisco IOS XR Software, and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause an affected device to reload. This vulnerability is due to improper input validation of the UDLD packets. An attacker could exploit this vulnerability by sending specifically crafted UDLD packets to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. Note: The UDLD feature is disabled by default, and the conditions to exploit this vulnerability are strict. An attacker must have full control of a directly connected device. On Cisco IOS XR devices, the impact is limited to the reload of the UDLD process.

A vulnerability in the Topology Discovery Service of Cisco One Platform Kit (onePK) in Cisco IOS Software, Cisco IOS XE Software, Cisco IOS XR Software, and Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to execute arbitrary code or cause a denial of service (DoS) condition on an affected device. The vulnerability is due to insufficient length restrictions when the onePK Topology Discovery Service parses Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol message to an affected device. An exploit could allow the attacker to cause a stack overflow, which could allow the attacker to execute arbitrary code with administrative privileges, or to cause a process crash, which could result in a reload of the device and cause a DoS condition.

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.

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

Cisco IOS XR allows remote attackers to cause a denial of service (RSVP process reload) via a malformed RSVP packet, aka Bug ID CSCub63710.

Cisco IOS XR allows remote attackers to cause a denial of service (LISP process reload) by establishing many LISP TCP sessions, aka Bug ID CSCuq90378.

Cisco IOS XR on ASR 9000 devices does not properly use compression for port-range and address-range encoding, which allows remote attackers to bypass intended Typhoon line-card ACL restrictions via transit traffic, aka Bug ID CSCup30133.

The CLI in Cisco IOS XR allows remote authenticated users to obtain sensitive information via unspecified commands, aka Bug IDs CSCuq42336, CSCuq76853, CSCuq76873, and CSCuq45383.

Cisco IOS XR on Trident line cards in ASR 9000 devices lacks a static punt policer, which allows remote attackers to cause a denial of service (CPU consumption) by sending many crafted packets, aka Bug ID CSCun83985.

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 PPTP-ALG component in CRS Carrier Grade Services Engine (CGSE) and ASR 9000 Integrated Service Module (ISM) in Cisco IOS XR allows remote attackers to cause a denial of service (module reset) via crafted packet streams, aka Bug ID CSCue91963.