CVE-2025-62496
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-10-16

Last updated on: 2025-10-28

Assigner: Google Inc.

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.
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Meta Information
Published
2025-10-16
Last Modified
2025-10-28
Generated
2026-05-07
AI Q&A
2025-10-16
EPSS Evaluated
2026-05-05
NVD
CVE-2025-62496
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
quickjs_project quickjs to 2025-09-13 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
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 occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability occurs in the QuickJS engine's BigInt string parsing function when it tries to create a BigInt from a very large string of digits. The function calculates the number of bits needed to store the BigInt, but for extremely large inputs, this calculation causes an integer overflow. This overflow results in an incorrect, smaller number of bits and memory limbs being allocated. Consequently, when the actual BigInt data is written, it exceeds the allocated buffer size, causing a heap out-of-bounds write.


How can this vulnerability impact me? :

The vulnerability can lead to a heap out-of-bounds write, which may cause memory corruption. This can potentially be exploited to execute arbitrary code, crash the application, or cause denial of service, depending on how the QuickJS engine is used within an application.


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