# CVE-2025-62494

## Summary

- **CVE ID:** CVE-2025-62494
- **Severity:** HIGH
- **CVSS Score:** 7.1 (CVSS:4.0/AV:A/AC:H/AT:P/PR:L/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L)
- **CWE:** CWE-704
- **Published:** Oct 16, 2025
- **Last Modified:** Mar 12, 2026

## Description

A type confusion vulnerability exists in the handling of the string addition (+) operation within the QuickJS engine.

  *  The code first checks if the left-hand operand is a string.


  *  It then attempts to convert the right-hand operand to a primitive value using JS_ToPrimitiveFree. This conversion can trigger a callback (e.g., toString or valueOf).


  *  During this callback, an attacker can modify the type of the left-hand operand in memory, changing it from a string to a different type (e.g., an object or an array).


  *  The code then proceeds to call JS_ConcatStringInPlace, which still treats the modified left-hand value as a string.


This mismatch between the assumed type (string) and the actual type allows an attacker to control the data structure being processed by the concatenation logic, resulting in a type confusion condition. This can lead to out-of-bounds memory access, potentially resulting in memory corruption and arbitrary code execution in the context of the QuickJS runtime.

## Affected Products

- QuickJS — QuickJS (2025-04-26)

## References

- [CNA](https://bellard.org/quickjs/Changelog)
- [CNA](https://issuetracker.google.com/434193023)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.48%
- **EPSS Percentile:** 39.9

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._