CVE-2025-62491 – Use-after-free in js_std_promise_rejection_check in QuickJS

CVE ID : CVE-2025-62491

Published : Oct. 16, 2025, 4:15 p.m. | 25 minutes ago

Description : 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.

Severity: 8.8 | HIGH

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