CVE-2025-62494

Summary

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 Software

Weaknesses

• CWE-704: CWE-704 Incorrect Type Conversion or Cast

ADP Enrichment

CISA ADP Vulnrichment

• SSVC:
• Exploitation: poc
  • Automatable: no
  • Technical Impact: total

References

• https://bellard.org/quickjs/Changelog
• https://issuetracker.google.com/434193023

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