Cisco patches three critical IOS XR flaws, advises immediate update
Cisco patched eight IOS XR vulnerabilities, including three critical ones, and is urging customers to apply updates.
The company detailed the issues in two advisories published Sept. 2, according to TechRadar. In one advisory, Cisco described seven vulnerabilities, including two critical bugs: CVE-2026-20274 and CVE-2026-20279, both rated 9.8 out of 10. CVE-2026-20274 is a network-based, low-complexity flaw that allows exploitation without authentication or user interaction; CVE-2026-20279 is an improper access control vulnerability with similar impact.
These two flaws and five others affect all releases of Cisco IOS XR Software, including IOS XR7 (LNT) Software, regardless of device configuration, the company said. There are no workarounds, so installing the provided patch is the only remedy.
The third critical vulnerability, CVE-2026-20212, was disclosed in a separate advisory. By successfully exploiting it, an attacker can connect to an affected device and send crafted input that could be executed as code without root privileges. Cisco said the issue could also cause the S1HAL process to crash, leading to a device reload.
This flaw affects Cisco Nexus 9000 Series Switches equipped with a Silicon One ASIC. As a mitigation, Cisco recommends using infrastructure access control lists (iACLs) to permit only required management and control-plane traffic, or to explicitly deny all TCP packets destined to a locally configured IP address with a destination port of 43210 or 43211.