PatchTheCVECVE-2021-4173: vim is vulnerable to Use After Free
52
This month
HIGH 7.8UPGRADEMITIGATEMITIGATE
CVE-2021-4173 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 | 2021-12-27 |
| Last modified | 2026-11-02 |
Last updated 2026-11-02 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
vim vim UPGRADE
Affected: < 8.2.3902
Fixed in: 8.2.3902
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy vim || rpm -q vim || vim --version
2. UPGRADE to 8.2.3902 (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.
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-2021-4173?
vim: upgrade to 8.2.3902; 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-2021-4173 being exploited?
CVE-2021-4173 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-2021-4173 affect?
CVE-2021-4173 affects vim, fedora, mac os x. Severity is high (CVSS 7.8). vim is vulnerable to Use After Free
How urgent is CVE-2021-4173?
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.