CVE-2021-39258
📋 TL;DR
CVE-2021-39258 is an out-of-bounds read vulnerability in NTFS-3G that allows attackers to read sensitive memory contents from a crafted NTFS image. This affects systems using NTFS-3G to mount NTFS filesystems, potentially exposing sensitive data. The vulnerability is triggered when processing malicious NTFS images.
💻 Affected Systems
- NTFS-3G
📦 What is this software?
Ntfs 3g by Tuxera
⚠️ Risk & Real-World Impact
Worst Case
Information disclosure leading to exposure of sensitive memory contents, potentially including credentials, encryption keys, or other confidential data from system memory.
Likely Case
Information disclosure from memory when processing malicious NTFS images, potentially revealing file system metadata or adjacent memory contents.
If Mitigated
Limited impact with proper access controls and untrusted NTFS image handling procedures in place.
🎯 Exploit Status
Exploitation requires user interaction to mount a malicious NTFS image. Proof-of-concept code exists in security advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2021.8.22
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 distributions: Use package manager (apt-get update && apt-get upgrade ntfs-3g for Debian/Ubuntu, yum update ntfs-3g for RHEL/CentOS). 3. For source installations: Download from https://github.com/tuxera/ntfs-3g/releases and compile.
🔧 Temporary Workarounds
Disable NTFS-3G mounting
linuxPrevent NTFS-3G from being used to mount NTFS filesystems
chmod -x /usr/bin/ntfs-3g
chmod -x /sbin/mount.ntfs-3g
Mount NTFS as read-only
linuxMount NTFS filesystems with read-only permissions to prevent exploitation
mount -t ntfs-3g -o ro /dev/device /mount/point
🧯 If You Can't Patch
- Restrict access to mount command to trusted users only
- Implement strict controls on mounting external NTFS devices and images
🔍 How to Verify
Check if Vulnerable:
Check NTFS-3G version: ntfs-3g --version | head -1Check Version:
ntfs-3g --version | head -1Verify Fix Applied:
Verify version is 2021.8.22 or later: ntfs-3g --version | grep -q '2021.8.22' && echo 'Patched'📡 Detection & Monitoring
Log Indicators:
- Failed mount attempts of NTFS filesystems
- Kernel logs showing filesystem errors
Network Indicators:
- Unusual file transfer activity preceding mount operations
SIEM Query:
source="syslog" AND "ntfs-3g" AND ("error" OR "failed" OR "corrupt")🔗 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://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://security.gentoo.org/glsa/202301-01
- https://www.debian.org/security/2021/dsa-4971
