CVE-2025-62494 — Type confusion in string addition in QuickJS
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 s…
Published: 2025-10-16 · CVSS: 7.1 · CVSS 4.0
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.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7