Security Resilience

CVE-2021-3156

Sudo Project Sudo 1.8.2 – 1.8.32

CISA KEVActive ExploitationEUVD ExploitedPublic PoC
Published
26 January 2021
Modified
10 November 2025
KEV Added
06 April 2022
Patch / advisory
View advisory
CVSS Score v3.1 7.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.99 100.0th percentile
Risk Priority 83 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2021-3156 is a high-severity Off-by-one Error (CWE-193) vulnerability in Sudo Project Sudo. Its CVSS base score is 7.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Data Obfuscation (T1001); ranked in the top 0.0% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

Sudo before version 1.9.5p2 is affected by an off-by-one error that produces a heap-based buffer overflow, tracked as CVE-2021-3156 and assigned CWE-193. The flaw resides in the command-line argument handling path used by sudoedit when invoked with the -s flag.

Local attackers who are already permitted to run sudoedit can trigger the overflow by supplying a command-line argument that terminates with a single backslash character, resulting in full root privilege escalation on the host. The vulnerability carries a CVSS 3.1 base score of 7.8 under the vector AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.

Public exploit code demonstrating the issue against multiple Sudo releases has been posted to Packet Storm, confirming that working proof-of-concept attacks exist for versions prior to the 1.9.5p2 fix.

EU & UK References

Vulnerability Data

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(s)
CWE-193
KEV Date Added
06 April 2022

Related Threats

Threat-Actor AttributionAI

Microsoft Corp. (Salesforce / Slack engineer recruitment claims)
2021 Top Routinely Exploited Vulnerabilities | CISA
AnonOps
2021 Top Routinely Exploited Vulnerabilities | CISA
CrowdStrike (McAfee / Symantec civil claims)
Russian Military Cyber Actors Target US and Global Critical Infrastructure | CISA
SentinelOne (Cylance / BlackBerry civil claims)
Russian Military Cyber Actors Target US and Global Critical Infrastructure | CISA
Ember Bear (G1003)
Russian Military Cyber Actors Target US and Global Critical Infrastructure | CISA

MITRE ATT&CK Enterprise Techniques

T1001 Data Obfuscation Command And Control
Adversaries may obfuscate command and control traffic to make it more difficult to detect.
attack.mitre.org →
T1001.003 Protocol or Service Impersonation Command And Control
Adversaries may impersonate legitimate protocols or web service traffic to disguise command and control activity and thwart analysis efforts.
attack.mitre.org →
T1003.001 LSASS Memory Credential Access
Adversaries may attempt to access credential material stored in the process memory of the Local Security Authority Subsystem Service (LSASS).
attack.mitre.org →
T1003.003 NTDS Credential Access
Adversaries may attempt to access or create a copy of the Active Directory domain database in order to steal credential information, as well as obtain other information about domain members such as devices, users, and access rights.
attack.mitre.org →
T1003.004 LSA Secrets Credential Access
Adversaries with SYSTEM access to a host may attempt to access Local Security Authority (LSA) secrets, which can contain a variety of different credential materials, such as credentials for service accounts.
attack.mitre.org →
T1003.006 DCSync Credential Access
Adversaries may attempt to access credentials and other sensitive information by abusing a Windows Domain Controller's application programming interface (API)(Citation: Microsoft DRSR Dec 2017) (Citation: Microsoft GetNCCChanges) (Citati…
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2019-0211Same product: Debian Debian Linuxboth on KEV
CVE-2024-1086Same product: Debian Debian Linuxboth on KEV
CVE-2023-28709Same product: Debian Debian Linux
CVE-2019-2215Same product: Debian Debian Linuxboth on KEV
CVE-2020-15999Same product: Debian Debian Linuxboth on KEV
CVE-2024-10442Same product: Synology Diskstation Manager
CVE-2023-4863Same product: Debian Debian Linuxboth on KEV
CVE-2023-4911Same product: Debian Debian Linuxboth on KEV
CVE-2022-0185Same product class: NAS / storage applianceboth on KEV
CVE-2022-0995Same product: Fedoraproject Fedoraboth on KEV

Affected Assets

sudo project
sudo
1.9.5 · 1.8.2 — 1.8.32 · 1.9.0 — 1.9.5
fedoraproject
fedora
32, 33
debian
debian linux
10.0, 9.0
netapp
active iq unified manager
all versions
netapp
cloud backup
all versions
netapp
hci management node
all versions
netapp
oncommand unified manager core package
all versions
netapp
ontap select deploy administration utility
all versions
netapp
ontap tools
9
netapp
solidfire
all versions
+14 more product configuration(s) — see NVD for full list

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V6.2.1

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 partial match
blocks

Secure SDLC practices directly prevent off-by-one errors via reviews, static analysis, and testing.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match
removes
A.5.15 Access control partial match
removes
A.5.16 Identity management partial match
removes
A.5.17 Authentication information partial match
removes
A.5.18 Access rights partial match
removes
A.8.10 Information deletion partial match
removes

References