Buffer over-read in Cisco IOS XE - CVE-2026-20311
Published: August 6, 2026
Vulnerability identifier: #VU141046
CSH Severity: Low
CVSS v4: 6 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-20311
CWE-ID: CWE-126
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote user to cause a denial of service.
The vulnerability exists due to insufficient error handling in the web-based management interface when authenticating with a malformed certificate. A remote user can authenticate with a malformed certificate to cause a denial of service.
Only devices with the HTTP Server feature and PIV-based authentication enabled are vulnerable. A successful exploit causes the affected device to reload.
Affected software
Cisco IOS XE
How to mitigate CVE-2026-20311
Install security update from vendor's website.
Cisco IOS XE - addressed in versions 17.12.8, 17.15.6, 17.18.4