CVE-2021-3974Public exploit

Process crash and memory corruption via stale pointer

Published Nov 19, 2021 · Updated Aug 3, 2024

Use-after-free in Vim before 8.2.3612 allows local users to crash the editor or corrupt memory through a mark-based NFA regular expression. In nfa_regmatch, getmark_buf can free the current line, but regexp_nfa.c continues through rex.line and rex.input without reacquiring that line. User interaction is required to run the crafted substitute expression; the stale pointer can terminate the Vim process or permit code execution in the user's context.

CVSS severity7.3
High
EPSS probability1.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Use-after-free in Vim before 8.2.3612 allows local users to crash the editor or corrupt memory through a mark-based NFA regular expression. In nfa_regmatch, getmark_buf can free the current line, but regexp_nfa.c continues through rex.line and rex.input without reacquiring that line. User interaction is required to run the crafted substitute expression; the stale pointer can terminate the Vim process or permit code execution in the user's context.

The record

CVE
CVE-2021-3974
Published
Nov 19, 2021
Updated
Aug 3, 2024
Vendor
Vim
Product
Vim
Classifications
CWE-416, T1203
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Nov 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <8.2.3612

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Vim · Vimversion=unspecified <8.2.3612

Published CVSS scores

7.3Protect AICVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-416Use After Free
T1203Exploitation for Client Execution

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo