CVE-2021-39254
📋 TL;DR
CVE-2021-39254 is an integer overflow vulnerability in NTFS-3G that can lead to heap-based buffer overflow when processing a malicious NTFS image. This could allow attackers to execute arbitrary code or cause denial of service. Systems using NTFS-3G versions before 2021.8.22 to mount NTFS filesystems are affected.
💻 Affected Systems
- NTFS-3G
- Tuxera NTFS-3G
- FUSE-based NTFS implementations
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Ntfs 3g by Tuxera
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with root privileges if attacker can supply a malicious NTFS image to a vulnerable system, potentially leading to complete system compromise.
Likely Case
Local privilege escalation or denial of service when users mount malicious NTFS drives or images, with potential for limited code execution.
If Mitigated
Denial of service with system crash or file corruption if exploit fails, but no code execution.
🎯 Exploit Status
Exploitation requires ability to mount a malicious NTFS image or drive. Proof of concept code exists in security advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2021.8.22 and later
Vendor Advisory: https://github.com/tuxera/ntfs-3g/security/advisories/GHSA-q759-8j5v-q5jp
Restart Required: No
Instructions:
1. Update NTFS-3G to version 2021.8.22 or later. 2. For Linux: Use package manager (apt-get update && apt-get upgrade ntfs-3g, yum update ntfs-3g, etc.). 3. For macOS: Update via Homebrew or download from Tuxera. 4. Recompile from source if using custom builds.
🔧 Temporary Workarounds
Disable NTFS mounting
linuxPrevent mounting of NTFS filesystems to eliminate attack surface
sudo rmmod fuse
sudo systemctl disable fuse
Remove NTFS-3G package: sudo apt-get remove ntfs-3g
Mount NTFS as read-only
linuxMount NTFS filesystems with read-only flag to prevent exploitation
mount -t ntfs-3g -o ro /dev/sdX1 /mnt/ntfs
🧯 If You Can't Patch
- Restrict NTFS mounting to trusted users only
- Implement strict access controls on devices that can be mounted
🔍 How to Verify
Check if Vulnerable:
Check NTFS-3G version: ntfs-3g --version | grep -i 'ntfs-3g'Check Version:
ntfs-3g --version | head -1Verify Fix Applied:
Verify version is 2021.8.22 or higher: ntfs-3g --version📡 Detection & Monitoring
Log Indicators:
- Kernel logs showing NTFS mount failures
- System crashes when mounting NTFS drives
- Unexpected process termination of mount.ntfs
Network Indicators:
- Unusual USB device mounting activity
- External drive mounting from untrusted sources
SIEM Query:
process_name="mount.ntfs" AND (event_type="process_crash" OR exit_code!=0)🔗 References
- https://github.com/tuxera/ntfs-3g/releases
- https://github.com/tuxera/ntfs-3g/security/advisories/GHSA-q759-8j5v-q5jp
- https://lists.debian.org/debian-lts-announce/2021/11/msg00013.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/766ISTT3KCARKFUIQT7N6WV6T63XOKG3/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HSEKTKHO5HFZHWZNJNBJZA56472KRUZI/
- https://security.gentoo.org/glsa/202301-01
- https://www.debian.org/security/2021/dsa-4971
- https://github.com/tuxera/ntfs-3g/releases
- https://github.com/tuxera/ntfs-3g/security/advisories/GHSA-q759-8j5v-q5jp
- https://lists.debian.org/debian-lts-announce/2021/11/msg00013.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/766ISTT3KCARKFUIQT7N6WV6T63XOKG3/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HSEKTKHO5HFZHWZNJNBJZA56472KRUZI/
- https://security.gentoo.org/glsa/202301-01
- https://www.debian.org/security/2021/dsa-4971
