CVE-2021-29952

What it actually does

Race condition during WebRender component destruction causes undefined behavior that can be leveraged for arbitrary code execution.

Why it matters to the business

Remote attackers could potentially gain full control of affected browser processes, leading to data theft or malware installation on user systems; the flaw is old with low exploitation probability and no known active campaigns.

How an attack unfolds

An attacker hosts a specially crafted webpage that forces rapid creation and destruction of WebRender components; the resulting race condition produces memory corruption that, with sufficient effort, can be turned into code execution inside the browser sandbox.

How to fix it

Upgrade Mozilla Firefox to version 88.0.1 or later and Firefox for Android to 88.1.3 or later; apply updates through the browser's built-in mechanism or package manager.

How to confirm the fix worked

Verify installed browser version meets or exceeds the fixed releases; confirm WebRender is enabled and test rendering paths with known benign workloads to ensure no crashes on component teardown.

Typical attack path

1. Deliver malicious webpage via phishing or compromised site
2. Trigger WebRender component lifecycle events that race during destruction
3. Exploit resulting undefined behavior to corrupt memory and execute attacker-controlled code

How to detect it

Review browser crash logs and telemetry for WebRender teardown anomalies; examine network logs for visits to previously unknown domains around the time of any suspicious process behavior.

What your security team should do

• Immediately deploy the listed browser updates across all managed endpoints
• Monitor for any post-update stability issues in WebRender workloads
• Review browser update policies to reduce future lag on security releases