CVE-2025-13020
📋 TL;DR
This CVE describes a use-after-free vulnerability in the WebRTC audio/video component of Mozilla products. It allows attackers to execute arbitrary code or cause denial of service by exploiting memory corruption after freeing. Affected users include anyone running vulnerable versions of Firefox, Firefox ESR, or Thunderbird.
💻 Affected Systems
- Firefox
- Firefox ESR
- Thunderbird
📦 What is this software?
Firefox by Mozilla
Firefox by Mozilla
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Browser/application crash (denial of service) or limited code execution within sandboxed context.
If Mitigated
Minimal impact if sandboxing works properly, potentially just application crash.
🎯 Exploit Status
Exploitation requires triggering specific WebRTC conditions but no authentication needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox 145+, Firefox ESR 140.5+, Thunderbird 145+, Thunderbird 140.5+
Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2025-87/
Restart Required: Yes
Instructions:
1. Open Firefox/Thunderbird. 2. Click menu → Help → About Firefox/Thunderbird. 3. Allow automatic update. 4. Restart when prompted. For enterprise: Deploy updated packages via your management system.
🔧 Temporary Workarounds
Disable WebRTC
allPrevents exploitation by disabling the vulnerable component.
about:config → media.peerconnection.enabled = false
Use content security policies
allRestrict WebRTC usage to trusted domains only.
Header: Content-Security-Policy: default-src 'self'; media-src 'self'
🧯 If You Can't Patch
- Isolate affected systems from untrusted networks and websites.
- Implement application allowlisting to prevent execution of malicious payloads.
🔍 How to Verify
Check if Vulnerable:
Check browser version in About dialog or via command: firefox --version | thunderbird --versionCheck Version:
firefox --version (Linux/macOS) or check About dialog (Windows)Verify Fix Applied:
Confirm version is Firefox ≥145, Firefox ESR ≥140.5, Thunderbird ≥145, or Thunderbird ≥140.5📡 Detection & Monitoring
Log Indicators:
- Browser crash logs with WebRTC/peerconnection references
- Memory access violation errors in application logs
Network Indicators:
- Unusual WebRTC STUN/TURN traffic patterns
- Suspicious media stream initiation
SIEM Query:
source="*firefox*" OR source="*thunderbird*" AND (error="segmentation fault" OR error="access violation" OR "peerconnection")