How severe is CVE-2021-3156?

CVE-2021-3156 has a CVSS score of 7.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-3156?

Affected package information for CVE-2021-3156 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2021-3156?

No fixed version has been published for CVE-2021-3156 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2021-3156 actively exploited in the wild?

Yes. There are 83 known exploit references for CVE-2021-3156, including 3 documented proof-of-concept exploits on Exploit-DB and 50 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-3156?

CVE-2021-3156 has an EPSS (Exploit Prediction Scoring System) score of 92.6%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2021-3156 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-3156 (Sudo Heap-Based Buffer Overflow Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2022-04-06. CISA required all US federal civilian agencies to remediate this vulnerability by 2022-04-27. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2021-3156?

CVE-2021-3156 is classified as CWE-193 (CWE-193). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-3156 published, and has it been updated?

CVE-2021-3156 was published on January 26, 2021 and was last updated on April 16, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2022-04-06 — agencies required to remediate by 2022-04-27

CVE-2021-3156

HIGH

Published

Jan 26, 2021

Updated

Apr 16, 2026

Affected

0 pkgs

Patched

None yet

Exploits

83 known

EPSS Exploitation Probability

via FIRST.org ↗

92.6%probability of exploitation in next 30 days

Very High Risk100th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

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.

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-49521localmultiple

Sudo 1.9.5p1 - 'Baron Samedit ' Heap-Based Buffer Overflow Privilege Escalation (1)

by West Shepherd · Feb 3, 2021

Exploit-DB Source

EDB-49522localmultiple

Sudo 1.9.5p1 - 'Baron Samedit ' Heap-Based Buffer Overflow Privilege Escalation (2)

by nu11secur1ty · Feb 3, 2021

Exploit-DB Source

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2021-3156 in your stack?

O3 detects CVE-2021-3156 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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