Is CVE-2021-3156 in the CISA KEV catalog?

Yes. CVE-2021-3156 is on the CISA Known Exploited Vulnerabilities list, added 2022-04-06.

What is the CVSS severity of CVE-2021-3156?

CVE-2021-3156 has a CVSS v3 base score of 7.8 (HIGH).

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

CVE-2021-3156 has an EPSS score of 99.30% (100th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-3156?

Upgrade sudo on debian 11 to 1.9.5p1-1.1 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2021-3156

HIGHCISA KEVEPSS 100th pctl

7.8

CVSS v3

NVD

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.

CWE-193

How to fix

Remediation Available

sudoDebian

Fixed in:1.9.5p1-1.1CVE-2021-3156

sudoUbuntu

Fixed in:1.8.9p5-1ubuntu1.5+esm6USN-4705-2

Fixed in:1.8.16-0ubuntu1.10USN-4705-1

Fixed in:1.8.21p2-3ubuntu1.4USN-4705-1

Fixed in:1.8.31-1ubuntu1.2USN-4705-1

sudo-ldapUbuntu

Fixed in:1.8.16-0ubuntu1.10USN-4705-1

Fixed in:1.8.21p2-3ubuntu1.4USN-4705-1

Fixed in:1.8.31-1ubuntu1.2USN-4705-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

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

Exploit Intelligence

99.30%probability of exploitation in 30 days

100thpercentile

Very high risk: more likely to be exploited than 100% of all known CVEs.

Known Exploited Vulnerability (CISA KEV)

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.

Apply updates per vendor instructions.

Remediation due: 2022-04-27

References

Related Vulnerabilities

Other CWE-193 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2003-0466	Critical	9.8	78%	-	-
CVE-2023-44444	High	7.8	56%	-	Fix
CVE-2021-23017	High	7.7	53%	-	Fix
CVE-2023-28709	High	7.5	52%	-	Fix
CVE-2018-8828	Critical	9.8	31%	-	Fix
CVE-2001-0609	Critical	9.8	18%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2025-11-10.