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 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.
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Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Thu, 16 Oct 2025 18:15:00 +0000
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Thu, 16 Oct 2025 16:00:00 +0000
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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 |
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Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: Google
Published:
Updated: 2025-10-16T17:26:25.654Z
Reserved: 2025-10-15T08:47:41.878Z
Link: CVE-2025-62496

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

Status : Received
Published: 2025-10-16T16:15:40.260
Modified: 2025-10-16T16:15:40.260
Link: CVE-2025-62496

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