CVE-2021-3974
📋 TL;DR
CVE-2021-3974 is a use-after-free vulnerability in Vim text editor that could allow an attacker to execute arbitrary code by tricking a user into opening a specially crafted file. This affects users who open untrusted files in Vim. The vulnerability exists in Vim's handling of certain memory operations.
💻 Affected Systems
- Vim
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Vim by Vim
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with the privileges of the user running Vim, potentially leading to full system compromise.
Likely Case
Local privilege escalation or arbitrary code execution when a user opens a malicious file.
If Mitigated
Limited impact if users only open trusted files and Vim runs with minimal privileges.
🎯 Exploit Status
Exploitation requires user interaction to open a malicious file. Proof-of-concept code is publicly available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Vim 8.2.3994 and later
Vendor Advisory: https://github.com/vim/vim/commit/64066b9acd9f8cffdf4840f797748f938a13f2d6
Restart Required: No
Instructions:
1. Update Vim using your system package manager (apt-get update && apt-get upgrade vim, yum update vim, etc.) 2. Alternatively, compile from source using the patched version from the Vim GitHub repository.
🔧 Temporary Workarounds
Restrict file opening
allConfigure Vim to only open files from trusted sources and avoid opening unknown files.
Use alternative editor
allTemporarily use a different text editor that is not affected by this vulnerability.
🧯 If You Can't Patch
- Run Vim with reduced privileges using sandboxing or containerization
- Implement strict file access controls and user training about opening untrusted files
🔍 How to Verify
Check if Vulnerable:
Run 'vim --version' and check if version is before 8.2.3994Check Version:
vim --version | head -1Verify Fix Applied:
Run 'vim --version' and confirm version is 8.2.3994 or later📡 Detection & Monitoring
Log Indicators:
- Unusual Vim process crashes
- Suspicious file access patterns in Vim
Network Indicators:
- None - this is a local file-based vulnerability
SIEM Query:
Process execution where command contains 'vim' and file path is from untrusted sources🔗 References
- http://www.openwall.com/lists/oss-security/2022/01/15/1
- https://github.com/vim/vim/commit/64066b9acd9f8cffdf4840f797748f938a13f2d6
- https://huntr.dev/bounties/e402cb2c-8ec4-4828-a692-c95f8e0de6d4
- https://lists.debian.org/debian-lts-announce/2022/03/msg00018.html
- https://lists.debian.org/debian-lts-announce/2022/11/msg00009.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FNXY7T5OORA7UJIMGSJBGHFMU6UZWS6P/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IH2LS2DXBTYOCWGAKFMBF3HTWWXPBEFL/
- https://security.gentoo.org/glsa/202208-32
- http://www.openwall.com/lists/oss-security/2022/01/15/1
- https://github.com/vim/vim/commit/64066b9acd9f8cffdf4840f797748f938a13f2d6
- https://huntr.dev/bounties/e402cb2c-8ec4-4828-a692-c95f8e0de6d4
- https://lists.debian.org/debian-lts-announce/2022/03/msg00018.html
- https://lists.debian.org/debian-lts-announce/2022/11/msg00009.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FNXY7T5OORA7UJIMGSJBGHFMU6UZWS6P/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IH2LS2DXBTYOCWGAKFMBF3HTWWXPBEFL/
- https://security.gentoo.org/glsa/202208-32
