Local memory corruption via oversized WASI stream read
Published Sep 7, 2026 · Updated Sep 8, 2026
Out-of-bounds write in Walrus commit af80e665ea49d9003695a66502f841ed1d8397e7 allows local users to corrupt memory via crafted WebAssembly. WASI 0.2 callWasiFunction allocates the actual read length but passes the requested length to memcpy, writing beyond the allocation when fewer bytes are returned. Execution of a malicious component is required; the overflow can crash the runtime or corrupt process memory, while further code execution is not demonstrated.
Summary
What happened
Out-of-bounds write in Walrus commit af80e665ea49d9003695a66502f841ed1d8397e7 allows local users to corrupt memory via crafted WebAssembly. WASI 0.2 callWasiFunction allocates the actual read length but passes the requested length to memcpy, writing beyond the allocation when fewer bytes are returned. Execution of a malicious component is required; the overflow can crash the runtime or corrupt process memory, while further code execution is not demonstrated.
The record
- CVE
- CVE-2026-86313
- Published
- Sep 7, 2026
- Updated
- Sep 8, 2026
- Vendor
- Samsung Electronics Co., Ltd.
- Product
- Walrus
- Classifications
- CWE-787, CAPEC-100, T1204.002
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 7, 2026CVE publishedPublication date reported by the CVE source.
- Sep 8, 2026Record 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=af80e665ea49d9003695a66502f841ed1d8397e7
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.
Weakness, pattern, technique
Public exploit references
- stream-read-oob-poc.wastproof of concept · demonstrated
- wasi-read-via-stream-offset-oob-write-poc.wastproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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