CVE-2025-62491 Use-after-free in js_std_promise_rejection_check in QuickJS
A use-after-free in QuickJS allows attackers to execute arbitrary code or cause denial of service via malicious JavaScript promise rejection handlers.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2025-62491?
CVE-2025-62491 is a high-severity use after free vulnerability in QuickJS, published on 16 Oct 2025. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-416
Which versions are affected by CVE-2025-62491?
It affects 1 product.
Products include Quickjs Project Quickjs.
How do I fix CVE-2025-62491?
No fix has been published for CVE-2025-62491 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2025-62491 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-62491 exists.
Other vulnerabilities in QuickJS
Sources
Also known as DEBIAN-CVE-2025-62491, GHSA-3r39-xffq-r9cc, UBUNTU-CVE-2025-62491.