QuickJS 0.9.0/3b45d15 integer overflow

Summaryinfo

A vulnerability was found in QuickJS. It has been rated as critical. This affects an unknown part. This manipulation causes integer overflow. This vulnerability is registered as CVE-2025-62496. Remote exploitation of the attack is possible. No exploit is available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as critical was found in QuickJS. Affected by this vulnerability is an unknown function. The manipulation with an unknown input leads to a integer overflow vulnerability. The CWE definition for the vulnerability is CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

A vulnerability exists in the QuickJS engine's BigInt string parsing logic (js_bigint_from_string) when attempting to create a BigInt from a string with an excessively large number of digits. The function calculates the necessary number of bits (n_bits) required to store the BigInt using the formula: $$\text{n\_bits} = (\text{n\_digits} \times 27 + 7) / 8 \quad (\text{for radix 10})$$ * For large input strings (e.g., $79,536,432$ digits or more for base 10), the intermediate calculation $(\text{n\_digits} \times 27 + 7)$ exceeds the maximum value of a standard signed 32-bit integer, resulting in an Integer Overflow. * The resulting n_bits value becomes unexpectedly small or even negative due to this wrap-around. * This flawed n_bits is then used to compute n_limbs, the number of memory "limbs" needed for the BigInt object. Since n_bits is too small, the calculated n_limbs is also significantly underestimated. * The function proceeds to allocate a JSBigInt object using this underestimated n_limbs. * When the function later attempts to write the actual BigInt data into the allocated object, the small buffer size is quickly exceeded, leading to a Heap Out-of-Bounds Write as data is written past the end of the allocated r->tab array.

The advisory is shared at bellard.org. This vulnerability is known as CVE-2025-62496 since 10/15/2025. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 270717 (Linux Distros Unpatched Vulnerability : CVE-2025-62496), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2025-09-13 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (270717). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Name

• QuickJS

Version

• 0.9.0
• 3b45d15

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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