CVE-2015-6673
📋 TL;DR
CVE-2015-6673 is a use-after-free vulnerability in libpgf's Decoder.cpp that allows attackers to execute arbitrary code or cause denial of service. This affects applications that process PGF image files using vulnerable versions of libpgf. The vulnerability can be triggered by parsing specially crafted PGF images.
💻 Affected Systems
- libpgf
- Applications using libpgf library
📦 What is this software?
Libpgf by Libpgf
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with the privileges of the application processing the PGF file, potentially leading to complete system compromise.
Likely Case
Application crash (denial of service) when processing malicious PGF files, with potential for code execution in some configurations.
If Mitigated
Limited to denial of service if exploit attempts are blocked or application runs with minimal privileges.
🎯 Exploit Status
Proof of concept exists in public references. Exploitation requires the target to process a malicious PGF file.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.15.32 and later
Vendor Advisory: https://sourceforge.net/p/libpgf/code/147/
Restart Required: Yes
Instructions:
1. Update libpgf to version 6.15.32 or later. 2. Recompile any applications using libpgf with the updated library. 3. Restart affected services or applications.
🔧 Temporary Workarounds
Disable PGF file processing
allConfigure applications to reject or not process PGF image files
Sandbox image processing
allRun applications that process PGF files in isolated containers or with reduced privileges
🧯 If You Can't Patch
- Implement strict input validation to reject suspicious PGF files
- Deploy application-level firewalls or WAF rules to block malicious PGF file uploads
🔍 How to Verify
Check if Vulnerable:
Check libpgf version: 'pgf --version' or check library version in package managerCheck Version:
pgf --version 2>/dev/null || dpkg -l | grep libpgf || rpm -qa | grep libpgfVerify Fix Applied:
Verify libpgf version is 6.15.32 or higher: 'pgf --version | grep -q "6.15.3[2-9]\|6\.1[6-9]\|[7-9]\.[0-9]"'📡 Detection & Monitoring
Log Indicators:
- Application crashes when processing image files
- Memory access violation errors in application logs
Network Indicators:
- Unexpected PGF file uploads to web applications
- Network traffic containing PGF files to vulnerable services
SIEM Query:
source="application.log" AND ("segmentation fault" OR "access violation" OR "libpgf")🔗 References
- http://www.openwall.com/lists/oss-security/2015/08/25/9
- https://bugzilla.redhat.com/show_bug.cgi?id=1251749
- https://lists.debian.org/debian-lts-announce/2019/12/msg00017.html
- https://security-tracker.debian.org/tracker/CVE-2015-6673/
- https://sourceforge.net/p/libpgf/code/147/
- https://sourceforge.net/p/libpgf/code/148/
- https://sourceforge.net/p/libpgf/code/HEAD/tree/trunk/libpgf/INSTALL
- https://usn.ubuntu.com/4554-1/
- http://www.openwall.com/lists/oss-security/2015/08/25/9
- https://bugzilla.redhat.com/show_bug.cgi?id=1251749
- https://lists.debian.org/debian-lts-announce/2019/12/msg00017.html
- https://security-tracker.debian.org/tracker/CVE-2015-6673/
- https://sourceforge.net/p/libpgf/code/147/
- https://sourceforge.net/p/libpgf/code/148/
- https://sourceforge.net/p/libpgf/code/HEAD/tree/trunk/libpgf/INSTALL
- https://usn.ubuntu.com/4554-1/
