Heap-data disclosure via unchecked cross-limb BigInt read
Published Oct 16, 2025 · Updated Oct 16, 2025
Out-of-bounds read in QuickJS 2025-04-26 allows attackers to disclose adjacent heap data through BigInt string conversion. In js_bigint_to_string1, an off-by-one digit count drives a cross-limb read of r->tab[pos + 1] without first proving that the limb exists. Exploitation requires code to convert a crafted BigInt with a susceptible radix; the resulting values can expose heap data but do not directly write memory.
Summary
What happened
Out-of-bounds read in QuickJS 2025-04-26 allows attackers to disclose adjacent heap data through BigInt string conversion. In js_bigint_to_string1, an off-by-one digit count drives a cross-limb read of r->tab[pos + 1] without first proving that the limb exists. Exploitation requires code to convert a crafted BigInt with a susceptible radix; the resulting values can expose heap data but do not directly write memory.
The record
- CVE
- CVE-2025-62493
- Published
- Oct 16, 2025
- Updated
- Oct 16, 2025
- Vendor
- Fabrice Bellard
- Product
- QuickJS
- Classifications
- CWE-125, CAPEC-175
- Attack vector
- adjacent
- Privileges
- authenticated
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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2025-04-26 <2025-09-13
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- Google Issue Tracker proof of conceptproof of concept · unverified
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Technologies
Your stack
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Your stack
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