CVE-2025-13013
📋 TL;DR
This CVE describes a mitigation bypass vulnerability in the DOM: Core & HTML component of Mozilla products. It allows attackers to bypass security mitigations, potentially leading to arbitrary code execution or privilege escalation. Affected users include those running vulnerable versions of Firefox, Firefox ESR, and Thunderbird.
💻 Affected Systems
- Firefox
- Firefox ESR
- Thunderbird
📦 What is this software?
Firefox by Mozilla
Firefox by Mozilla
Firefox by Mozilla
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise via arbitrary code execution with user privileges, potentially leading to data theft, ransomware deployment, or lateral movement.
Likely Case
Limited impact such as browser sandbox escape, session hijacking, or data exfiltration from the browser context.
If Mitigated
Minimal impact if proper network segmentation, endpoint protection, and least privilege principles are enforced.
🎯 Exploit Status
Exploitation requires user interaction (visiting malicious website or opening malicious email). No public exploit code available at disclosure.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox 145+, Firefox ESR 140.5+, Firefox ESR 115.30+, Thunderbird 145+, Thunderbird 140.5+
Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2025-87/
Restart Required: Yes
Instructions:
1. Open affected application (Firefox/Thunderbird). 2. Click menu → Help → About Firefox/Thunderbird. 3. Application will automatically check for and install updates. 4. Restart application when prompted.
🔧 Temporary Workarounds
Disable JavaScript
allTemporarily disable JavaScript to prevent exploitation via malicious websites
about:config → javascript.enabled = false
Use Content Security Policy
allImplement strict CSP headers to limit script execution
Content-Security-Policy: script-src 'self'
🧯 If You Can't Patch
- Network segmentation to isolate vulnerable systems from critical assets
- Implement application allowlisting to prevent unauthorized code execution
🔍 How to Verify
Check if Vulnerable:
Check application version in About dialog (menu → Help → About Firefox/Thunderbird)Check Version:
firefox --version or thunderbird --versionVerify Fix Applied:
Verify version is equal to or greater than patched versions: Firefox 145+, Firefox ESR 140.5+, Firefox ESR 115.30+, Thunderbird 145+, Thunderbird 140.5+📡 Detection & Monitoring
Log Indicators:
- Unusual process creation from browser processes
- Suspicious network connections from browser
Network Indicators:
- Unexpected outbound connections from browser to unknown IPs
- DNS queries to suspicious domains
SIEM Query:
process_name:firefox.exe AND (parent_process:explorer.exe OR command_line:*powershell*)🔗 References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1991945
- https://www.mozilla.org/security/advisories/mfsa2025-87/
- https://www.mozilla.org/security/advisories/mfsa2025-88/
- https://www.mozilla.org/security/advisories/mfsa2025-89/
- https://www.mozilla.org/security/advisories/mfsa2025-90/
- https://www.mozilla.org/security/advisories/mfsa2025-91/
