CVE-2026-2772
📋 TL;DR
A use-after-free vulnerability in Firefox's audio/video playback component allows attackers to execute arbitrary code or cause crashes. This affects Firefox versions below 148, Firefox ESR below 115.33, and Firefox ESR below 140.8. Users running these vulnerable versions are at risk when 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 full system compromise, data theft, or ransomware deployment.
Likely Case
Browser crash or denial of service, potentially enabling further exploitation through chained vulnerabilities.
If Mitigated
Limited impact with browser sandboxing and exploit mitigations; likely crash without code execution.
🎯 Exploit Status
Use-after-free vulnerabilities typically require precise memory manipulation but can be exploited via JavaScript in web pages.
🛠️ 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 download and installation. 4. Restart Firefox when prompted.
🔧 Temporary Workarounds
Disable JavaScript
allPrevents exploitation via web pages but breaks most website functionality.
about:config → javascript.enabled = false
Use Content Security Policy
allRestrict media sources to trusted domains only.
Header set Content-Security-Policy "media-src 'self' https://trusted.example.com"
🧯 If You Can't Patch
- Restrict browser usage to trusted websites only.
- Implement network filtering to block malicious domains and scripts.
🔍 How to Verify
Check if Vulnerable:
Check Firefox version in menu → Help → About Firefox. If version is below 148 (or ESR below specified versions), system is vulnerable.Check Version:
firefox --versionVerify Fix Applied:
Confirm version is Firefox 148 or higher, or ESR 115.33/140.8 or higher after update.📡 Detection & Monitoring
Log Indicators:
- Browser crash logs with memory access violations
- Unexpected process termination in system logs
Network Indicators:
- Requests to known exploit domains
- Unusual media file downloads
SIEM Query:
source="firefox.log" AND ("crash" OR "access violation") OR destination_ip IN (malicious_ip_list)🔗 References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2014827
- 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/
