CVE-2026-2760
📋 TL;DR
This CVE describes a sandbox escape vulnerability in Firefox's WebRender graphics component due to incorrect boundary conditions. It allows attackers to break out of browser security sandboxes and potentially execute arbitrary code. Affected users include anyone running vulnerable versions of Firefox, Firefox ESR 115.x, or Firefox ESR 140.x.
💻 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
Complete system compromise with attacker gaining full control of the affected system, potentially leading to data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Limited sandbox escape allowing attacker to execute code with user privileges, potentially leading to credential theft, browser session hijacking, or installation of malware.
If Mitigated
Attack contained within browser sandbox with no system-level impact if proper security controls like application sandboxing and least privilege are enforced.
🎯 Exploit Status
Exploitation requires user interaction (visiting malicious website) but no authentication. Sandbox escape vulnerabilities typically require chaining with other exploits for full impact.
🛠️ 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 menu > Help > About Firefox. 2. Browser will automatically check for updates. 3. If update available, click 'Restart to update Firefox'. 4. For enterprise deployments, use Firefox ESR deployment tools or update through standard patch management.
🔧 Temporary Workarounds
Disable WebRender
allTemporarily disable the WebRender graphics component to mitigate the vulnerability
about:config
Set gfx.webrender.all to false
Set gfx.webrender.enabled to false
Enable Enhanced Security Settings
allConfigure Firefox with stricter security settings to limit potential impact
about:config
Set security.sandbox.content.level to 4
Set privacy.trackingprotection.enabled to true
🧯 If You Can't Patch
- Implement network filtering to block known malicious domains and restrict browser access to trusted sites only
- Deploy application control solutions to prevent execution of unauthorized binaries from browser processes
🔍 How to Verify
Check if Vulnerable:
Check Firefox version via about:support or Help > About Firefox. Compare against affected versions.Check Version:
firefox --version (Linux/macOS) or check Help > About Firefox (Windows)Verify Fix Applied:
Verify Firefox version is 148 or higher, or Firefox ESR is 115.33/140.8 or higher. Check about:config for gfx.webrender.all and ensure it's true only if intentionally enabled.📡 Detection & Monitoring
Log Indicators:
- Unusual browser process spawning child processes
- Browser crashes with memory access violations
- Suspicious file writes from browser processes
Network Indicators:
- Unexpected outbound connections from browser to unknown IPs
- DNS requests to newly registered or suspicious domains
SIEM Query:
process_name:firefox.exe AND (process_parent:unusual OR file_write:*.exe OR network_connection:malicious_ip)🔗 References
- https://bugzilla.mozilla.org/show_bug.cgi?id=2011062
- 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/
