CVE-2025-8736
📋 TL;DR
A critical buffer overflow vulnerability exists in GNU cflow's lexer component (yylex function in c.c) affecting versions up to 1.8. This allows local attackers to execute arbitrary code or cause denial of service. The vulnerability requires local access to the system running vulnerable cflow software.
💻 Affected Systems
- GNU cflow
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Local privilege escalation leading to full system compromise, arbitrary code execution as the user running cflow, or complete system crash.
Likely Case
Denial of service (cflow crashes) or limited code execution within the context of the user running cflow.
If Mitigated
Minimal impact if proper privilege separation exists and cflow runs with minimal privileges.
🎯 Exploit Status
Exploit has been publicly disclosed according to references. Requires local access and ability to provide malicious input to cflow.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version after 1.8 (check GNU cflow repository for latest)
Vendor Advisory: https://lists.gnu.org/archive/html/bug-cflow/2025-07/msg00001.html
Restart Required: No
Instructions:
1. Check GNU cflow repository for latest version. 2. Download and compile from source. 3. Replace existing cflow binary. 4. Verify installation with version check.
🔧 Temporary Workarounds
Restrict cflow usage
allLimit cflow execution to trusted users only and avoid processing untrusted input files.
chmod 750 /usr/bin/cflow
setfacl -m u:trusteduser:rx /usr/bin/cflow
Use alternative tools
allTemporarily use alternative call graph generators until patched.
🧯 If You Can't Patch
- Run cflow with minimal privileges (non-root user, restricted capabilities)
- Implement strict input validation for files processed by cflow
🔍 How to Verify
Check if Vulnerable:
Check cflow version: cflow --version. If version is 1.8 or earlier, system is vulnerable.Check Version:
cflow --versionVerify Fix Applied:
After updating, run cflow --version to confirm version is newer than 1.8. Test with known safe input files.📡 Detection & Monitoring
Log Indicators:
- Segmentation fault messages from cflow
- Abnormal termination of cflow processes
- Core dumps from cflow
Network Indicators:
- Not applicable - local vulnerability
SIEM Query:
process_name:"cflow" AND (event_type:"segfault" OR exit_code:139)