CVE-2015-9381
📋 TL;DR
This vulnerability is a heap-based buffer over-read in FreeType's Type 1 font parser. It allows attackers to read sensitive memory contents, potentially leading to information disclosure or as a stepping stone for further attacks. Any system or application using vulnerable FreeType versions to process Type 1 fonts is affected.
💻 Affected Systems
- FreeType
- Applications/libraries using FreeType (e.g., browsers, PDF readers, image processors)
📦 What is this software?
Freetype by Freetype
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if combined with other vulnerabilities, or sensitive memory disclosure including passwords, keys, or other confidential data.
Likely Case
Application crash (denial of service) or limited information disclosure from heap memory, potentially exposing font-related data or adjacent memory contents.
If Mitigated
Application crash with no data loss if proper sandboxing/privilege separation exists, or blocked exploitation due to input validation/sanitization.
🎯 Exploit Status
Exploitation requires processing a malicious Type 1 font file. Public proof-of-concept code exists in the bug reports and commit history. Weaponization is likely given the CVSS score and buffer over-read nature.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: FreeType 2.6.1 and later
Vendor Advisory: https://access.redhat.com/errata/RHSA-2019:4254
Restart Required: Yes
Instructions:
1. Update FreeType to version 2.6.1 or later using your system's package manager. 2. For Linux: Use 'sudo apt update && sudo apt upgrade freetype' (Debian/Ubuntu) or 'sudo yum update freetype' (RHEL/CentOS). 3. For Windows: Update through vendor channels or recompile applications with patched FreeType. 4. Restart affected applications or services.
🔧 Temporary Workarounds
Disable Type 1 font processing
allConfigure applications to disable Type 1 font parsing if not needed.
Application-specific configuration; no universal command
Use application sandboxing
linuxRun vulnerable applications in sandboxed environments to limit impact.
firejail --net=none application_name
bubblewrap --unshare-all --die-with-parent application_name
🧯 If You Can't Patch
- Implement strict input validation to block malicious font files before processing.
- Use network segmentation to isolate systems processing untrusted fonts from critical assets.
🔍 How to Verify
Check if Vulnerable:
Check FreeType version: 'freetype-config --version' or 'dpkg -l | grep freetype' on Linux. If version is below 2.6.1, system is vulnerable.Check Version:
freetype-config --version 2>/dev/null || dpkg -l | grep freetype 2>/dev/null || rpm -q freetype 2>/dev/null || echo 'Check system documentation'Verify Fix Applied:
After update, verify version is 2.6.1 or higher using same commands. Test with known malicious Type 1 font samples if available.📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults or memory errors when processing fonts
- Unexpected font parsing errors in application logs
Network Indicators:
- Unusual font file downloads or transfers to systems with vulnerable applications
SIEM Query:
source="application_logs" AND ("segmentation fault" OR "memory error" OR "font parse")🔗 References
- http://git.savannah.gnu.org/cgit/freetype/freetype2.git/commit/src/type1/t1parse.c?id=7962a15d64c876870ca0ae435ea2467d9be268d9
- https://access.redhat.com/errata/RHSA-2019:4254
- https://lists.debian.org/debian-lts-announce/2019/09/msg00002.html
- https://savannah.nongnu.org/bugs/?45955
- https://usn.ubuntu.com/4126-2/
- http://git.savannah.gnu.org/cgit/freetype/freetype2.git/commit/src/type1/t1parse.c?id=7962a15d64c876870ca0ae435ea2467d9be268d9
- https://access.redhat.com/errata/RHSA-2019:4254
- https://lists.debian.org/debian-lts-announce/2019/09/msg00002.html
- https://savannah.nongnu.org/bugs/?45955
- https://usn.ubuntu.com/4126-2/
