CVE-2026-2770
📋 TL;DR
This CVE describes a use-after-free vulnerability in Firefox's DOM Bindings (WebIDL) component that could allow an attacker to execute arbitrary code. It affects Firefox versions below 148, Firefox ESR below 115.33, and Firefox ESR below 140.8. Attackers could exploit this by tricking users into visiting malicious websites.
💻 Affected Systems
- Mozilla Firefox
- Mozilla Firefox ESR
📦 What is this software?
Firefox by Mozilla
Firefox by Mozilla
Firefox by Mozilla
Thunderbird by Mozilla
Thunderbird by Mozilla
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Browser crash (denial of service) or limited code execution within browser sandbox.
If Mitigated
No impact if patched or if browser security features block exploitation.
🎯 Exploit Status
Use-after-free vulnerabilities typically require specific memory manipulation techniques but can be exploited via JavaScript.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8
Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2026-13/
Restart Required: Yes
Instructions:
1. Open Firefox. 2. Click menu → Help → About Firefox. 3. Allow automatic update to complete. 4. Restart Firefox when prompted.
🔧 Temporary Workarounds
Disable JavaScript
allPrevents exploitation by disabling JavaScript execution in browser.
about:config → javascript.enabled = false
Use Content Security Policy
allRestrict script execution to trusted sources only.
Add 'Content-Security-Policy: script-src 'self'' to web server headers
🧯 If You Can't Patch
- Restrict browser to trusted websites only using network policies.
- Implement application whitelisting to prevent unauthorized code execution.
🔍 How to Verify
Check if Vulnerable:
Check Firefox version in About Firefox dialog or via 'firefox --version' command.Check Version:
firefox --versionVerify Fix Applied:
Confirm version is Firefox ≥148, Firefox ESR ≥115.33, or Firefox ESR ≥140.8.📡 Detection & Monitoring
Log Indicators:
- Browser crash logs with memory access violations
- Unexpected browser process termination
Network Indicators:
- Requests to known malicious domains from Firefox
- Unusual outbound connections after visiting websites
SIEM Query:
source="firefox.log" AND ("crash" OR "access violation" OR "segmentation fault")🔗 References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2014585
- https://www.mozilla.org/security/advisories/mfsa2026-13/
- https://www.mozilla.org/security/advisories/mfsa2026-14/
- https://www.mozilla.org/security/advisories/mfsa2026-15/
- https://www.mozilla.org/security/advisories/mfsa2026-16/
- https://www.mozilla.org/security/advisories/mfsa2026-17/
