CVE-2026-2798
📋 TL;DR
This CVE describes a use-after-free vulnerability in Firefox's DOM Core & HTML components that could allow attackers to execute arbitrary code or cause crashes. It affects Firefox versions before 148. Users running vulnerable Firefox versions are at risk when visiting malicious websites.
💻 Affected Systems
- Mozilla Firefox
📦 What is this software?
Firefox 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 or denial of service, potentially enabling further exploitation through chained vulnerabilities.
If Mitigated
Limited impact with proper sandboxing and security controls in place, potentially just browser instability.
🎯 Exploit Status
Use-after-free vulnerabilities typically require specific memory manipulation knowledge but can be reliably exploited once understood.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox 148
Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2026-13/
Restart Required: Yes
Instructions:
1. Open Firefox. 2. Click menu → Help → About Firefox. 3. Firefox will check for updates and install Firefox 148. 4. Restart Firefox when prompted.
🔧 Temporary Workarounds
Disable JavaScript
allTemporarily disable JavaScript to prevent exploitation via malicious websites
about:config → javascript.enabled → false
Use Enhanced Tracking Protection Strict
allEnable strict tracking protection to block more potentially malicious content
Settings → Privacy & Security → Enhanced Tracking Protection → Strict
🧯 If You Can't Patch
- Restrict browser usage to trusted websites only
- Implement network filtering to block access to known malicious domains
🔍 How to Verify
Check if Vulnerable:
Check Firefox version: about:support → Application Basics → Version. If version is less than 148, you are vulnerable.Check Version:
firefox --version (Linux/macOS) or check about:support (all platforms)Verify Fix Applied:
Verify Firefox version is 148 or higher in about:support after update.📡 Detection & Monitoring
Log Indicators:
- Firefox crash reports with memory access violations
- Unexpected browser termination events
- DOM manipulation errors in console logs
Network Indicators:
- Unusual outbound connections after visiting websites
- Traffic to known exploit kit domains
SIEM Query:
source="firefox.logs" AND (event_type="crash" OR error="use-after-free" OR error="memory_access")