Heap corruption via wrapped bytecode allocation size
Published Sep 24, 2026 · Updated Sep 24, 2026
Out-of-bounds write in QuickJS 2026-06-04 allows context-dependent attackers to corrupt heap memory through crafted bytecode. JS_ReadFunctionTag decodes closure_var_count and cpool_count into signed integers, then casts negative values into allocation-size arithmetic that wraps below the object header before memcpy writes past the heap buffer. Exploitation requires an embedder to pass untrusted serialized bytecode to JS_ReadObject; the published reproducer causes a deterministic crash, while code execution remains unproven.
Summary
What happened
Out-of-bounds write in QuickJS 2026-06-04 allows context-dependent attackers to corrupt heap memory through crafted bytecode. JS_ReadFunctionTag decodes closure_var_count and cpool_count into signed integers, then casts negative values into allocation-size arithmetic that wraps below the object header before memcpy writes past the heap buffer. Exploitation requires an embedder to pass untrusted serialized bytecode to JS_ReadObject; the published reproducer causes a deterministic crash, while code execution remains unproven.
The record
- CVE
- CVE-2026-88378
- Published
- Sep 24, 2026
- Updated
- Sep 24, 2026
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-787, T1499
- Attack vector
- Unavailable
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 24, 2026CVE publishedPublication date reported by the CVE source.
- Sep 24, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
Published CVSS scores
No CVSS assessment is available in this record.
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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.
Activity data is delayed. The latest report is Sep 28, 2026.
Public exploit references
- JS_ReadObject 21-byte crash reproducerproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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