CVE-2021-3156: Sudo Heap-Based Buffer Overflow Vulnerability

CISA Known Exploited Vulnerabilities

Name

Sudo Heap-Based Buffer Overflow Vulnerability

Vendor

Sudo

Product

Sudo

Added to the catalog

2022-04-06

Due date for US federal agencies

2022-04-27

Weaknesses

CWE-122, CWE-193

Catalog version

2026.10.30

Sudo contains an off-by-one error that can result in a heap-based buffer overflow, which allows for privilege escalation.

Required action (CISA)

Apply updates per vendor instructions.

Ransomware use: CISA does not mark known use of this vulnerability in ransomware campaigns.

Links in CISA's notes

• https://nvd.nist.gov/vuln/detail/CVE-2021-3156

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2021-01-26T21:15:12.987

Last modified

2026-06-17T04:04:45.830

Weaknesses

CWE-193

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.

References

• http://packetstormsecurity.com/files/161160/Sudo-Heap-Based-Buffer-Overflow.html (Exploit, Third Party Advisory, VDB Entry)
• http://packetstormsecurity.com/files/161230/Sudo-Buffer-Overflow-Privilege-Escalation.html (Exploit, Third Party Advisory, VDB Entry)
• http://packetstormsecurity.com/files/161270/Sudo-1.9.5p1-Buffer-Overflow-Privilege-Escalation.html (Exploit, Third Party Advisory, VDB Entry)
• http://packetstormsecurity.com/files/161293/Sudo-1.8.31p2-1.9.5p1-Buffer-Overflow.html (Exploit, Third Party Advisory, VDB Entry)
• http://packetstormsecurity.com/files/176932/glibc-syslog-Heap-Based-Buffer-Overflow.html (Exploit, Third Party Advisory, VDB Entry)
• http://seclists.org/fulldisclosure/2021/Feb/42 (Mailing List, Third Party Advisory)
• http://seclists.org/fulldisclosure/2021/Jan/79 (Exploit, Mailing List, Third Party Advisory)
• http://seclists.org/fulldisclosure/2024/Feb/3 (Exploit, Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/01/26/3 (Exploit, Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/01/27/1 (Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/01/27/2 (Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/02/15/1 (Exploit, Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/09/14/2 (Mailing List, Patch, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2024/01/30/6 (Exploit, Mailing List)
• http://www.openwall.com/lists/oss-security/2024/01/30/8 (Mailing List)
• https://kc.mcafee.com/corporate/index?page=content&id=SB10348 (Broken Link, Third Party Advisory)
• https://lists.debian.org/debian-lts-announce/2021/01/msg00022.html (Mailing List, Third Party Advisory)
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CALA5FTXIQBRRYUA2ZQNJXB6OQMAXEII/ (Mailing List, Release Notes)
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LHXK6ICO5AYLGFK2TAX5MZKUXTUKWOJY/ (Mailing List, Release Notes)
• https://security.gentoo.org/glsa/202101-33 (Third Party Advisory)
• https://security.netapp.com/advisory/ntap-20210128-0001/ (Third Party Advisory)
• https://security.netapp.com/advisory/ntap-20210128-0002/ (Third Party Advisory)
• https://support.apple.com/kb/HT212177 (Third Party Advisory)
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sudo-privesc-jan2021-qnYQfcM (Third Party Advisory)
• https://www.beyondtrust.com/blog/entry/security-advisory-privilege-management-for-unix-linux-pmul-basic-and-privilege-management-for-mac-pmm-affected-by-sudo-vulnerability (Third Party Advisory)
• https://www.debian.org/security/2021/dsa-4839 (Third Party Advisory)
• https://www.kb.cert.org/vuls/id/794544 (Third Party Advisory, US Government Resource)
• https://www.openwall.com/lists/oss-security/2021/01/26/3 (Exploit, Mailing List, Third Party Advisory)
• https://www.oracle.com//security-alerts/cpujul2021.html (Patch, Third Party Advisory)
• https://www.oracle.com/security-alerts/cpuapr2022.html (Patch, Third Party Advisory)
• https://www.oracle.com/security-alerts/cpuoct2021.html (Patch, Third Party Advisory)
• https://www.sudo.ws/stable.html#1.9.5p2 (Release Notes)
• https://www.synology.com/security/advisory/Synology_SA_21_02 (Third Party Advisory)
• https://www.vicarius.io/vsociety/posts/sudoedit-pwned-cve-2021-3156 (Exploit, Third Party Advisory)
• http://packetstormsecurity.com/files/161160/Sudo-Heap-Based-Buffer-Overflow.html (Exploit, Third Party Advisory, VDB Entry)
• http://packetstormsecurity.com/files/161230/Sudo-Buffer-Overflow-Privilege-Escalation.html (Exploit, Third Party Advisory, VDB Entry)
• http://packetstormsecurity.com/files/161270/Sudo-1.9.5p1-Buffer-Overflow-Privilege-Escalation.html (Exploit, Third Party Advisory, VDB Entry)
• http://packetstormsecurity.com/files/161293/Sudo-1.8.31p2-1.9.5p1-Buffer-Overflow.html (Exploit, Third Party Advisory, VDB Entry)
• http://packetstormsecurity.com/files/176932/glibc-syslog-Heap-Based-Buffer-Overflow.html (Exploit, Third Party Advisory, VDB Entry)
• http://seclists.org/fulldisclosure/2021/Feb/42 (Mailing List, Third Party Advisory)
• http://seclists.org/fulldisclosure/2021/Jan/79 (Exploit, Mailing List, Third Party Advisory)
• http://seclists.org/fulldisclosure/2024/Feb/3 (Exploit, Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/01/26/3 (Exploit, Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/01/27/1 (Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/01/27/2 (Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/02/15/1 (Exploit, Mailing List, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2021/09/14/2 (Mailing List, Patch, Third Party Advisory)
• http://www.openwall.com/lists/oss-security/2024/01/30/6 (Exploit, Mailing List)
• http://www.openwall.com/lists/oss-security/2024/01/30/8 (Mailing List)
• https://kc.mcafee.com/corporate/index?page=content&id=SB10348 (Broken Link, Third Party Advisory)
• https://lists.debian.org/debian-lts-announce/2021/01/msg00022.html (Mailing List, Third Party Advisory)
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CALA5FTXIQBRRYUA2ZQNJXB6OQMAXEII/ (Mailing List, Release Notes)
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LHXK6ICO5AYLGFK2TAX5MZKUXTUKWOJY/ (Mailing List, Release Notes)
• https://security.gentoo.org/glsa/202101-33 (Third Party Advisory)
• https://security.netapp.com/advisory/ntap-20210128-0001/ (Third Party Advisory)
• https://security.netapp.com/advisory/ntap-20210128-0002/ (Third Party Advisory)
• https://support.apple.com/kb/HT212177 (Third Party Advisory)
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-sudo-privesc-jan2021-qnYQfcM (Third Party Advisory)
• https://www.beyondtrust.com/blog/entry/security-advisory-privilege-management-for-unix-linux-pmul-basic-and-privilege-management-for-mac-pmm-affected-by-sudo-vulnerability (Third Party Advisory)
• https://www.debian.org/security/2021/dsa-4839 (Third Party Advisory)
• https://www.kb.cert.org/vuls/id/794544 (Third Party Advisory, US Government Resource)
• https://www.openwall.com/lists/oss-security/2021/01/26/3 (Exploit, Mailing List, Third Party Advisory)
• https://www.oracle.com//security-alerts/cpujul2021.html (Patch, Third Party Advisory)
• https://www.oracle.com/security-alerts/cpuapr2022.html (Patch, Third Party Advisory)
• https://www.oracle.com/security-alerts/cpuoct2021.html (Patch, Third Party Advisory)
• https://www.sudo.ws/stable.html#1.9.5p2 (Release Notes)
• https://www.synology.com/security/advisory/Synology_SA_21_02 (Third Party Advisory)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3156 (US Government Resource)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:41:51.476Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-3156

CVE record

Assigner

mitre

State

PUBLISHED

Published

2021-01-26T00:00:00.000Z

Updated

2025-10-21T23:35:29.600Z

Problem types

n/a

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.

References

• [debian-lts-announce] 20210126 [SECURITY] [DLA 2534-1] sudo security update
• 20210126 Baron Samedit: Heap-based buffer overflow in Sudo (CVE-2021-3156)
• [oss-security] 20210126 Baron Samedit: Heap-based buffer overflow in Sudo (CVE-2021-3156)
• GLSA-202101-33
• DSA-4839
• FEDORA-2021-2cb63d912a
• FEDORA-2021-8840cbdccd
• [oss-security] 20210127 Re: Baron Samedit: Heap-based buffer overflow in Sudo (CVE-2021-3156)
• [oss-security] 20210127 Re: Baron Samedit: Heap-based buffer overflow in Sudo (CVE-2021-3156)
• 20210129 Sudo Privilege Escalation Vulnerability Affecting Cisco Products: January 2021
• VU#794544
• 20210211 APPLE-SA-2021-02-09-1 macOS Big Sur 11.2.1, macOS Catalina 10.15.7 Supplemental Update, and macOS Mojave 10.14.6 Security Update 2021-002
• [oss-security] 20210215 Re: sudo: Ineffective NO_ROOT_MAILER and Baron Samedit
• https://www.oracle.com//security-alerts/cpujul2021.html
• https://www.sudo.ws/stable.html#1.9.5p2
• https://www.openwall.com/lists/oss-security/2021/01/26/3
• http://packetstormsecurity.com/files/161160/Sudo-Heap-Based-Buffer-Overflow.html
• https://security.netapp.com/advisory/ntap-20210128-0002/
• https://security.netapp.com/advisory/ntap-20210128-0001/
• http://packetstormsecurity.com/files/161230/Sudo-Buffer-Overflow-Privilege-Escalation.html
• http://packetstormsecurity.com/files/161270/Sudo-1.9.5p1-Buffer-Overflow-Privilege-Escalation.html
• http://packetstormsecurity.com/files/161293/Sudo-1.8.31p2-1.9.5p1-Buffer-Overflow.html
• https://support.apple.com/kb/HT212177
• https://kc.mcafee.com/corporate/index?page=content&id=SB10348
• https://www.beyondtrust.com/blog/entry/security-advisory-privilege-management-for-unix-linux-pmul-basic-and-privilege-management-for-mac-pmm-affected-by-sudo-vulnerability
• https://www.synology.com/security/advisory/Synology_SA_21_02
• [oss-security] 20210914 Re: Oracle Solaris membership in the distros list
• https://www.oracle.com/security-alerts/cpuoct2021.html
• https://www.oracle.com/security-alerts/cpuapr2022.html
• [oss-security] 20240130 Re: CVE-2023-6246: Heap-based buffer overflow in the glibc's syslog()
• [oss-security] 20240130 CVE-2023-6246: Heap-based buffer overflow in the glibc's syslog()
• http://packetstormsecurity.com/files/176932/glibc-syslog-Heap-Based-Buffer-Overflow.html
• 20240204 CVE-2023-6246: Heap-based buffer overflow in the glibc's syslog()
• https://www.vicarius.io/vsociety/posts/sudoedit-pwned-cve-2021-3156

Read on 2026-11-03T01:07:54.531Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/3xxx/CVE-2021-3156.json

Detection rules (SigmaHQ)

SigmaHQ rules whose own tags name this CVE. Each rule page shows the rule as its author published it.

• CVE-2021-3156 Exploitation Attempt (status unsupported, level high)
• CVE-2021-3156 Exploitation Attempt Bruteforcing (status unsupported, level high)

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/