CVE-2025-62491 Affecting quickjs package, versions *

Note: Versions mentioned in the description apply only to the upstream quickjs package and not the quickjs package as distributed by Debian. See How to fix? for Debian:13 relevant fixed versions and status.

A Use-After-Free (UAF) vulnerability exists in the QuickJS engine's standard library when iterating over the global list of unhandled rejected promises (ts->rejected_promise_list).

• The function js_std_promise_rejection_check attempts to iterate over the rejected_promise_list to report unhandled rejections using a standard list loop.

• The reason for a promise rejection is processed inside the loop, including calling js_std_dump_error1(ctx, rp->reason).

• If the promise rejection reason is an Error object that defines a custom property getter (e.g., via Object.defineProperty), this getter is executed during the error dumping process.

• The malicious custom getter can execute JavaScript code that calls catch() on the same rejected promise being processed.

• Calling catch() internally triggers js_std_promise_rejection_tracker, which then removes and frees the current promise entry (JSRejectedPromiseEntry) from the rejected_promise_list.

• Since the list iteration continues using the now-freed memory pointer (el), the subsequent loop access results in a Use-After-Free condition.

• https://security-tracker.debian.org/tracker/CVE-2025-62491
• https://bellard.org/quickjs/Changelog
• https://issuetracker.google.com/434195203