CVE-2021-4166Public exploit

Editor crash via unlocked argument-list mutation

Published Dec 25, 2021 · Updated Aug 3, 2024

Out-of-bounds read in Vim before 8.2.3884 allows context-dependent attackers to crash the editor through argument-list mutation. During :all processing, do_arg_all() iterates the active argument list without locking it, so a WinNew autocommand can clear the list and leave the loop reading invalid entries. Execution requires attacker-influenced commands or configuration that changes the argument list during :all; the grounded upstream impact is a process crash.

CVSS severity7.1
High
EPSS probability1.58%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in Vim before 8.2.3884 allows context-dependent attackers to crash the editor through argument-list mutation. During :all processing, do_arg_all() iterates the active argument list without locking it, so a WinNew autocommand can clear the list and leave the loop reading invalid entries. Execution requires attacker-influenced commands or configuration that changes the argument list during :all; the grounded upstream impact is a process crash.

The record

CVE
CVE-2021-4166
Published
Dec 25, 2021
Updated
Aug 3, 2024
Vendor
Vim
Product
Vim
Classifications
CWE-125
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 25, 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

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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 privilegesunauthenticated

What is affected?

Vim · Vimversion=unspecified <8.2

Published CVSS scores

7.1NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
7.1huntr.devCVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H
5.8NIST NVDAV:N/AC:M/Au:N/C:P/I:N/A:P

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-125Out-of-bounds Read

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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