CVE-2025-62490: quickjs Use-After-Free — Exploit

Description

In quickjs, in js_print_object, when printing an array, the function first fetches the array length and then loops over it. The issue is, printing a value is not side-effect free. An attacker-defined callback could run during js_print_value, during which the array could get resized and len1 become out of bounds. This results in a use-after-free.A second instance occurs in the same function during printing of a map or set objects. The code iterates over ms->records list, but once again, elements could be removed from the list during js_print_value call.

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CVSS v3.1 Score

8.8

HIGH

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-416 Use After Free

Affected Products

Vendor	Product	Versions
quickjs_project	quickjs	< 2025-09-13

References

Exploits

https://issuetracker.google.com/434196651

Other References

https://bellard.org/quickjs/Changelog

Frequently Asked Questions

What is CVE-2025-62490? +

In quickjs, in js_print_object, when printing an array, the function first fetches the array length and then loops over it. The issue is, printing a value is not side-effect free. An attacker-defined callback could run during js_print_value, during which the array could get resized and len1 become out of bounds. This results in a use-after-free.A second instance occurs in the same function during printing of a map or set objects. The code iterates over ms->records list, but once again, elements could be removed from the list during js_print_value call. It has a CVSS v3.1 base score of 8.8 (HIGH).

How severe is CVE-2025-62490? +

CVE-2025-62490 has a CVSS v3.1 score of 8.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-62490? +

CVE-2025-62490 affects products from quickjs_project, specifically: quickjs. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-62490? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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