CVE-2021-4187: vim is vulnerable to Use After Free

Q: How do I fix CVE-2021-4187?

vim: upgrade to newer than 8.2.3912; fedora: mitigate or apply the listed mitigation; mac os x: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-4187 being exploited?

CVE-2021-4187 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-4187 affect?

CVE-2021-4187 affects vim, fedora, mac os x. Severity is high (CVSS 7.8). vim is vulnerable to Use After Free

Q: How urgent is CVE-2021-4187?

Priority 52/100. High severity; Public exploit reference

This month

HIGH 7.8UPGRADEMITIGATEMITIGATE

CVE-2021-4187 is a high-severity flaw (CVSS 7.8) affecting vim, fedora, mac os x. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

vim is vulnerable to Use After Free

Why this priority

High severity
Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.8% (top 22%)
CISA exploited list	No
Weakness	CWE-416
Published	2021-12-29
Last modified	2026-11-02

Publisher (CNA): huntr.dev · Vendor: apple · fedoraproject · vim

Last updated 2026-11-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-12-29 17:15 UTCPublished CVE record published
2026-11-02 19:17 UTCUpdated Record last modified

vim vim UPGRADE

Affected: <= 8.2.3912

Fixed in: newer than 8.2.3912

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy vim || rpm -q vim || vim --version

2. UPGRADE to newer than 8.2.3912 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade vim

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade vim

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

fedoraproject fedora MITIGATE

Affected: 34 · 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 34

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

apple mac os x MITIGATE

Affected: 10.15.7 · 10.15.7 security_update_2020-001 · 10.15.7 security_update_2021-001 · 10.15.7 security_update_2021-002 · 10.15.7 security_update_2021-003 · 10.15.7 security_update_2021-004 · 10.15.7 security_update_2021-005 · 10.15.7 security_update_2021-006

Fixed in: no fixed release known

Safe to downgrade to: a release before 10.15.7

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

apple macos UPGRADE

Affected: < 12.3 · >= 11.0 and < 11.6.6 · 10.15.7 security_update_2022-004

Fixed in: 11.6.6, 12.3

Safe to downgrade to: a release before 10.15.7

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-4187?

vim: upgrade to newer than 8.2.3912; fedora: mitigate or apply the listed mitigation; mac os x: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-4187 being exploited?

CVE-2021-4187 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-4187 affect?

CVE-2021-4187 affects vim, fedora, mac os x. Severity is high (CVSS 7.8). vim is vulnerable to Use After Free

How urgent is CVE-2021-4187?

Priority 52/100. High severity; Public exploit reference

Software pages

macOS vulnerabilities · Vim vulnerabilities

Related CVEs

CVE-2022-3235 HIGH 7.8 UPGRADE MITIGATE Use After Free in GitHub repository vim/vim prior to 9.0.0490.
CVE-2022-3234 HIGH 7.8 UPGRADE MITIGATE Heap-based Buffer Overflow in GitHub repository vim/vim prior to 9.0.0483.
CVE-2022-3153 MEDIUM 5.5 UPGRADE NULL Pointer Dereference in GitHub repository vim/vim prior to 9.0.0404.
CVE-2022-3134 HIGH 7.8 UPGRADE UPGRADE Use After Free in GitHub repository vim/vim prior to 9.0.0389.
CVE-2022-3099 HIGH 7.8 UPGRADE MITIGATE Use After Free in GitHub repository vim/vim prior to 9.0.0360.

References

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