CVE-2021-3156Known exploitationPublic exploit

Root privilege escalation via sudoedit argument unescaping

Published Jan 26, 2021 · Updated Oct 21, 2025

Heap-based buffer overflow in sudo 1.8.2 through 1.8.31p2 and 1.9.0 through 1.9.5p1 allows local users to gain root privileges. The set_cmnd() path allocates user_args from escaped argument lengths, then unescapes a trailing backslash and copies bytes excluded from the allocation size. Any local user able to execute sudoedit can trigger the flaw under the default configuration without sudoers membership or a password.

CVSS severity7.8
High
EPSS probability99.97%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in sudo 1.8.2 through 1.8.31p2 and 1.9.0 through 1.9.5p1 allows local users to gain root privileges. The set_cmnd() path allocates user_args from escaped argument lengths, then unescapes a trailing backslash and copies bytes excluded from the allocation size. Any local user able to execute sudoedit can trigger the flaw under the default configuration without sudoers membership or a password.

The record

CVE
CVE-2021-3156
Published
Jan 26, 2021
Updated
Oct 21, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-122, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 21, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8Red HatCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8CVE.orgCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationReported
Public exploitPublished

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
T1068Exploitation for Privilege Escalation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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