CVE-2023-29549

What it actually does

A call to the JavaScript bind function can resolve to an incorrect realm, allowing code running inside JavaScript-implemented sandboxes such as SES to obtain references outside the intended isolation boundary.

Why it matters to the business

Attackers may be able to bypass client-side isolation protections in affected browsers, increasing the chance that malicious web content can access or alter data it should not reach.

How an attack unfolds

An attacker serves a web page containing crafted JavaScript that invokes bind under conditions that trigger the realm mismatch; if the page is rendered in an SES-style sandbox the incorrect realm may expose privileged objects, enabling further actions such as reading cross-origin data or executing code with elevated privileges.

How to fix it

Upgrade Mozilla Firefox to version 112 or later and Mozilla Focus for Android to version 112 or later. Where immediate updates are not possible, restrict use of JavaScript sandboxes such as SES and apply browser content-blocking extensions.

How to confirm the fix worked

Confirm browser version is 112 or newer via the about:support page or equivalent; test that SES or similar sandbox libraries correctly isolate code after the upgrade.

Typical attack path

1. Attacker hosts malicious page or injects script into a trusted site
2. Victim opens the page in an affected Firefox or Focus build
3. JavaScript executes and calls bind in a way that selects the wrong realm
4. Sandbox isolation is violated, granting access to objects outside the intended compartment
5. Attacker leverages the escape to perform unauthorized actions within the browser context

How to detect it

Review browser process logs and crash reports for unexpected realm transitions or sandbox violations; examine web server access logs for pages known to trigger bind-related behavior in vulnerable builds.

What your security team should do

• Prioritize deployment of Firefox 112+ and Focus 112+ across all managed endpoints
• Monitor EPSS and exploit maturity signals for any increase in observed activity
• Review reliance on client-side JavaScript sandboxes and consider server-side alternatives where feasible