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High · 8.8 CVE-2025-62491 EUVD-2025-34783GHSA-3r39-xffq-r9cc

Use-after-free in js_std_promise_rejection_check in QuickJS

Published Oct 16, 2025 · Updated Oct 16, 2025 · Assigned by Google

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.

Affected products

VendorProductAffectedFixed
QuickJS QuickJS 2025-04-26 – < 2025-09-13 2025-09-13

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 quickjs No fix yet —
Debian 13 quickjs No fix yet —
ReleasePackageFixed inAdvisory
Ubuntu 26.10 quickjs No fix yet —
Ubuntu 25.10 quickjs No fix yet —
Show 1 more (older releases, extended support, other products)
ReleasePackageFixed inAdvisory
Ubuntu Pro 24.04 LTS quickjs No fix yet —

References