Sudo Heap-Based Buffer Overflow Vulnerability
Sudo contains an off-by-one error that can result in a heap-based buffer overflow, which allows for privilege escalation.
- Vendor
- Sudo
- Product
- Sudo
- CVSS
- 7.8
- EPSS (exploit probability)
- 100.0%
- Status
- kev
- CISA patch-by (BOD 22-01)
- Added to KEV
Is CVE-2021-3156 being exploited?
Yes. CISA added CVE-2021-3156 to its Known Exploited Vulnerabilities catalog on . CISA only lists a CVE when it has reliable evidence of exploitation in the wild.
FIRST's EPSS model puts the probability of exploitation activity in the next 30 days at 100.0% (scored October 14, 2026).
- CISA KEV[ LISTED ]
- ENISA EUVD (exploited)[ — ]
- CIRCL KEV[ — ]
Catalog snapshot 2026-10-25. Full cross-catalog view: /kev-comparison
CVE-2021-3156 timeline
Every event links to its source. Catalog dates are each catalog's own; day offsets count from NVD publication. Data: JSON
What to do
CISA required actionApply updates per vendor instructions.
US federal civilian agencies must remediate by (21 days after listing) under BOD 22-01. Everyone else: that deadline is a sensible upper bound, not a target. Vendor guidance and the NVD record are linked under Source above.
Other Sudo CVEs we track
| CVE / Vulnerability | Severity | CVSS | EPSS | Added to KEV |
|---|---|---|---|---|
| CVE-2025-32463 Sudo Inclusion of Functionality from Untrusted Control Sphere Vulnerability | [ CRITICAL ] | 9.3 | 55.5% |