CVE-2021-34720: Cisco IOS XR

High severity, CVSS 8.6. EPSS: 1.3% chance of exploitation in the next 30 days.

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.

Affected products

• Cisco IOS XR: before 6.2.3 (fixed in 6.2.3); from 6.3.0, before 6.3.2 (fixed in 6.3.2); from 6.5.0, before 7.2.2 (fixed in 7.2.2)

Published 2021-09-09. Last modified 2026-06-17.