CVE-2021-3156

Sudo: Heap-Based Buffer Overflow

As of , CVE-2021-3156 in Sudo is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch this week.

Exploited
Yes: CISA listed it on 6 April 2022
US federal deadline
27 April 202221 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
Not known to CISA
EPSS score
0.99Higher than 99% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
EPSS when listed
0.59 on 6 April 2022EPSS on the day CISA listed it.
Public exploit
1 Metasploit module and 2 Exploit-DB entries
Fix
No vendor link in CISA's entry

What CISA says to do

Apply updates per vendor instructions.

CISA's required action

What the flaw is

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

CISA's 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.

The CVE record's description, from mitre

CVE published
26 January 2021
Assigned by
mitre
CVSS
7.8 High (CVSS 3.1, from CISA-ADP)
CWE-193
Off-by-one Error
CWE-122
Heap-based Buffer Overflow
CISA SSVC, exploitation
active
CISA SSVC, automatable
no
CISA SSVC, technical impact
total

Timeline

  1. The CVE record was published.
  2. Exploit-DB published an exploit (EDB-ID 49521).
  3. Exploit-DB published an exploit (EDB-ID 49522).
  4. CISA added it to its list of exploited vulnerabilities.
  5. The US federal deadline to fix it.

Public exploits

Facts from Metasploit's module list and Exploit-DB's index; we never copy exploit code.

Sudo: other exploited entries

VulnerabilityProductOur groupListedDeadlineEPSS
CVE-2025-32463Inclusion of Functionality from Untrusted Control SphereSudo SudoPatch this weekMetasploit module; EPSS 0.550.55

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