CVE-2021-3156: Sudo Sudo exploited

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

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.

Description quoted from the CVE record (assigned by mitre, published 2021-01-26).

Weakness: CWE-193 Off-by-one Error

How it can be exploited

Exploitable with local access with low attack complexity needing low privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: no. Technical impact: total.

On CISA KEV since: 2022-04-06
US federal deadline: 2022-04-27
Ransomware use: Not known

Public exploit evidence (Exploit Observer)

Exploit Observer found 2 Exploit-DB entries, 1 Nuclei template, 103 code repositories and 11 research write-ups naming this CVE.

Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.

See all 133 references on Exploit Observer

Live scores

EPSS: 1.000
very likely to be attacked soon
VEDAS: 0.984
strong exploit evidence
On CISA KEV: Yes, since 2022-04-06
Detection rule: Out of scope (local)

EPSS (chance of attack)

VEDAS (exploit evidence)

Thin horizontal line: the “likely exploited” threshold (EPSS 0.10, VEDAS 0.5). Shaded “no data” areas are periods when cve-scores did not publish.

Who is affected

Product	Affected	Not affected
Not stated	versions not stated in the record	Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

How to fix it

CISA required action: Apply updates per vendor instructions.

Vendor guidance:

GLSA-202101-33 (vendor-advisory)
DSA-4839 (vendor-advisory)
FEDORA-2021-2cb63d912a (vendor-advisory)
FEDORA-2021-8840cbdccd (vendor-advisory)
20210129 Sudo Privilege Escalation Vulnerability Affecting Cisco Products: January 2021 (vendor-advisory)

How to detect it

This bug needs local access to exploit. VEDAS signatures cover remotely exploitable bugs for now, so there is no network rule or remote check for it. Patch it and watch your endpoint telemetry for unusual local activity.

Advisories on this CVE

ARTEX AI pentest operators exposed their own servers, revealing an agentic hacking campaign against South Korean banks (full advisory)

References

Vendor advisories and patches

GLSA-202101-33 (vendor-advisory)
DSA-4839 (vendor-advisory)
FEDORA-2021-2cb63d912a (vendor-advisory)
FEDORA-2021-8840cbdccd (vendor-advisory)
20210129 Sudo Privilege Escalation Vulnerability Affecting Cisco Products: January 2021 (vendor-advisory)

Technical analysis and advisories

VU#794544 (third-party-advisory)

Government sources

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3156 (government-resource)

Other references

16 more

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.