Memory corruption via overflowing BigInt size calculation
Published Oct 16, 2025 · Updated Oct 16, 2025
Heap out-of-bounds write in QuickJS 2025-04-26 allows attackers to corrupt memory via an excessively long decimal BigInt string. js_bigint_from_string multiplies the digit count by 27 in a signed 32-bit calculation; overflow understates n_bits and n_limbs, so later writes exceed the allocated r->tab array. Exploitation requires the host to parse roughly 79.5 million decimal digits as a BigInt, and the resulting process memory corruption can cause a crash or alter execution.
Summary
What happened
Heap out-of-bounds write in QuickJS 2025-04-26 allows attackers to corrupt memory via an excessively long decimal BigInt string. js_bigint_from_string multiplies the digit count by 27 in a signed 32-bit calculation; overflow understates n_bits and n_limbs, so later writes exceed the allocated r->tab array. Exploitation requires the host to parse roughly 79.5 million decimal digits as a BigInt, and the resulting process memory corruption can cause a crash or alter execution.
The record
- CVE
- CVE-2025-62496
- Published
- Oct 16, 2025
- Updated
- Oct 16, 2025
- Vendor
- Fabrice Bellard
- Product
- QuickJS
- Classifications
- CWE-190, T1203
- Attack vector
- adjacent
- Privileges
- Unavailable
Timeline
How it unfolded
- Oct 16, 2025CVE publishedPublication date reported by the CVE source.
- Oct 16, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=2025-04-26 <2025-09-13
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What is affected?
Published CVSS scores
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Attacks
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Technologies
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Your stack
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