CVE-2026-0879
📋 TL;DR
This CVE describes a sandbox escape vulnerability in the Graphics component of Mozilla products due to incorrect boundary conditions. Attackers could exploit this to break out of browser sandboxes and execute arbitrary code with higher privileges. It affects Firefox, Firefox ESR, and Thunderbird users running vulnerable versions.
💻 Affected Systems
- Firefox
- Firefox ESR
- Thunderbird
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through sandbox escape leading to arbitrary code execution with user or system-level privileges, potentially enabling malware installation, data theft, or ransomware deployment.
Likely Case
Sandbox escape allowing attackers to execute code with elevated privileges, potentially leading to browser hijacking, credential theft, or installation of malicious extensions.
If Mitigated
Limited impact if proper sandboxing and privilege separation are maintained; exploitation would be contained within browser process boundaries.
🎯 Exploit Status
Boundary condition vulnerabilities typically require crafted input but can be exploited without authentication through web content. No public exploit code is mentioned in the references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox 147, Firefox ESR 115.32, Firefox ESR 140.7, Thunderbird 147, Thunderbird 140.7
Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2026-01/
Restart Required: Yes
Instructions:
1. Open Firefox/Thunderbird. 2. Click menu → Help → About Firefox/Thunderbird. 3. The browser will check for updates and prompt to install. 4. Restart the application after update completes. For enterprise deployments, use your standard patch management system.
🔧 Temporary Workarounds
Disable JavaScript
allTemporarily disable JavaScript to reduce attack surface while patching
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
- Isolate vulnerable browsers in separate network segments with restricted internet access
- Implement application whitelisting to prevent execution of unauthorized processes
🔍 How to Verify
Check if Vulnerable:
Check browser version in About Firefox/Thunderbird menu and compare with affected versions listCheck Version:
firefox --version or thunderbird --version on Linux; Check About menu on Windows/macOSVerify Fix Applied:
Verify version is equal to or greater than patched versions: Firefox 147+, Firefox ESR 115.32+, Firefox ESR 140.7+, Thunderbird 147+, Thunderbird 140.7+📡 Detection & Monitoring
Log Indicators:
- Unusual process creation from browser processes
- Sandbox violation events in security logs
- Browser crash reports with memory corruption signatures
Network Indicators:
- Connections to known malicious domains from browser processes
- Unusual outbound traffic patterns from user workstations
SIEM Query:
process_name="firefox.exe" AND (event_id=4688 OR parent_process_name="firefox.exe")🔗 References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2004602
- https://www.mozilla.org/security/advisories/mfsa2026-01/
- https://www.mozilla.org/security/advisories/mfsa2026-02/
- https://www.mozilla.org/security/advisories/mfsa2026-03/
- https://www.mozilla.org/security/advisories/mfsa2026-04/
- https://www.mozilla.org/security/advisories/mfsa2026-05/
