CVE-2021-4187Public exploit

Editor crash via split nested-function arguments

Published Dec 29, 2021 · Updated Nov 3, 2025

Use-after-free in Vim 8.2.0695 through 8.2.3922 allows local users to crash the editor by sourcing a crafted Vim9 script. In get_function_args(), a split nested-function argument list frees the previous command line without retargeting cmdlinep, leaving the same allocation to be freed again. Exploitation requires a user to source or compile attacker-controlled Vim9 code; the upstream proof demonstrates a process crash, while code execution is not established.

CVSS severity7.8
High
EPSS probability1.63%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Vim 8.2.0695 through 8.2.3922 allows local users to crash the editor by sourcing a crafted Vim9 script. In get_function_args(), a split nested-function argument list frees the previous command line without retargeting cmdlinep, leaving the same allocation to be freed again. Exploitation requires a user to source or compile attacker-controlled Vim9 code; the upstream proof demonstrates a process crash, while code execution is not established.

The record

CVE
CVE-2021-4187
Published
Dec 29, 2021
Updated
Nov 3, 2025
Vendor
Vim
Product
Vim
Classifications
CWE-416, T1203
Attack vector
local
Privileges
Unavailable

Timeline

How it unfolded

  1. Dec 29, 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

What conditions does exploitation require?

Attack vectorlocal
Required privilegesUnavailable in this record.

What is affected?

Vim · Vimversion=unspecified <8.2

Published CVSS scores

6.8huntr.devCVSS:3.0/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:H
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

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 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

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Your stack

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