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CVE-2021-3156

High CVSS 7.8 Known exploited

Published 2021-01-26 · last changed 2026-06-17 · added to CISA KEV 2022-04-06

This one is being exploited in the wild.

CISA added CVE-2021-3156 to the Known Exploited Vulnerabilities catalog on 2022-04-06. Federal agencies are required to remediate it on a deadline. If you have affected machines, this is the class of finding that moves ahead of the rest of the queue.

The fix

We hold no Microsoft remediation data for CVE-2021-3156, which normally means it is not a Windows CVE. For non-Microsoft software the fix is the vendor's own updated release, and the affected versions are listed below.

What it is

Sudo before 1.9.5p2 contains an off-by-one error that can result in a heap-based buffer overflow, which allows privilege escalation to root via "sudoedit -s" and a command-line argument that ends with a single backslash character.

Sources

CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H