CVE-2021-4019Public exploit

Process crash via unbounded help argument copy

Published Dec 1, 2021 · Updated Nov 3, 2025

Heap-based buffer overflow in Vim before 8.2.3669 allows local users to crash the editor by supplying a long help argument. In find_help_tags() in src/help.c, consecutive STRCPY calls append the argument to a fixed IOSIZE buffer without enforcing its length. Triggering the overflow requires local execution of Vim's help command with a crafted argument; the demonstrated consequence is a process crash.

CVSS severity7.8
High
EPSS probability1.79%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap-based buffer overflow in Vim before 8.2.3669 allows local users to crash the editor by supplying a long help argument. In find_help_tags() in src/help.c, consecutive STRCPY calls append the argument to a fixed IOSIZE buffer without enforcing its length. Triggering the overflow requires local execution of Vim's help command with a crafted argument; the demonstrated consequence is a process crash.

The record

CVE
CVE-2021-4019
Published
Dec 1, 2021
Updated
Nov 3, 2025
Vendor
Vim
Product
Vim
Classifications
CWE-122, CWE-787, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 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?

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

  1. Affected versionversion=unspecified <8.2.3669

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Vim · Vimversion=unspecified <8.2.3669

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.1huntr.devCVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-122Heap-based Buffer Overflow
CWE-787Out-of-bounds Write
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

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Your stack

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