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Exploited vulnerability · CISA KEV

Is CVE-2021-3156 exploited? Yes: in CISA KEV since 6 Apr 2022

Gociux · Sudo · data: CISA KEV, CVE record, FIRST EPSS

Yes. CVE-2021-3156, Sudo Heap-Based Buffer Overflow Vulnerability, is being exploited in the wild. CISA added it to its Known Exploited Vulnerabilities catalog on 6 Apr 2022, 435 days after it was published. It affects Sudo. If you run it, CISA's required action is: Apply updates per vendor instructions.

exploitedYesCISA KEV · 6 Apr 2022
ransomwareNot knownno confirmed use
EPSStop 1%among the most likely CVEs to be exploited
severity7.8CVSS 3.1 · high
US federal due27 Apr 2022BOD 22-01 deadline

What it is

Sudo contains an off-by-one error that can result in a heap-based buffer overflow, which allows for privilege escalation.

VendorSudo (2 exploited CVEs in KEV)
ProductSudo
VulnerabilitySudo Heap-Based Buffer Overflow Vulnerability
WeaknessCWE-122, CWE-193
Published26 Jan 2021
Added to KEV6 Apr 2022
Reported by (CNA)mitre

What to do

  1. Check whether you run it. Look for Sudo in your asset inventory, including appliances and cloud images. Stack check lists every exploited Sudo CVE at once.
  2. Apply the fix. Apply updates per vendor instructions.
  3. If you can't patch today, take the affected service off the internet or restrict who can reach it, and check its logs for signs of compromise since 26 Jan 2021.
  4. Get told next time. Email alerts when CISA adds a CVE for Sudo.

Other exploited CVEs in Sudo

References

Questions

Is CVE-2021-3156 being exploited?

Yes. CISA added CVE-2021-3156 to the Known Exploited Vulnerabilities catalog on 6 Apr 2022, which means there is reliable evidence of exploitation in the wild.

Is CVE-2021-3156 used in ransomware attacks?

CISA does not list known ransomware use for it. That can change, and exploitation alone is reason to fix it first.

How do I fix CVE-2021-3156?

Apply updates per vendor instructions. Check Sudo's advisory for the fixed versions, and if you can't patch quickly, restrict access to the affected Sudo and watch it for signs of compromise.

Sources: CISA KEV (exploitation, ransomware use, required action, due date), the CVE record (publication date, CVSS, CNA), NVD and FIRST EPSS (live score). More: all KEV additions in April 2022 · Sudo scorecard · act-now radar.

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