# 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.

- **Severity:** High 8.8 (`CVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L`)
- **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 available:** No
- **Published:** 16 Oct 2025
- **Updated:** 16 Oct 2025
- **Also known as:** DEBIAN-CVE-2025-62491, GHSA-3r39-xffq-r9cc, UBUNTU-CVE-2025-62491

## 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 (Use After Free)

## Which versions are affected by CVE-2025-62491?

It affects 1 product.


Products: 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.

## 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

- [CVE-2025-62490](https://insights.sbomify.com/CVE-2025-62490/): Use-after-free in js_print_object in QuickJS (high 8.8)
- [CVE-2025-69654](https://insights.sbomify.com/CVE-2025-69654/): Denial of service in n/a (high 7.5)
- [CVE-2023-48183](https://insights.sbomify.com/CVE-2023-48183/): Null dereference in n/a (high 7.5)
- [CVE-2023-31922](https://insights.sbomify.com/CVE-2023-31922/): Denial of service in n/a (high 7.5)
- [CVE-2020-22876](https://insights.sbomify.com/CVE-2020-22876/): Memory corruption in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-62491 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-62491 exists.

Affected product: QuickJS. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-62491/ (Markdown: https://insights.sbomify.com/CVE-2025-62491/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-62491
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-62491
- OSV: https://osv.dev/vulnerability/CVE-2025-62491

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-62491/
Summaries are generated and may contain mistakes; the official description above is the record.