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.
Advisories

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Fixes

Solution

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Workaround

No workaround given by the vendor.

History

Thu, 16 Oct 2025 18:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Thu, 16 Oct 2025 16:00:00 +0000

Type Values Removed Values Added
Description 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.
Title Integer overflow in js_bigint_from_string in QuickJS
Weaknesses CWE-190
References
Metrics cvssV4_0

{'score': 7.1, 'vector': '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: Google

Published:

Updated: 2025-10-16T17:26:25.654Z

Reserved: 2025-10-15T08:47:41.878Z

Link: CVE-2025-62496

cve-icon Vulnrichment

Updated: 2025-10-16T17:26:22.279Z

cve-icon NVD

Status : Received

Published: 2025-10-16T16:15:40.260

Modified: 2025-10-16T16:15:40.260

Link: CVE-2025-62496

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.