Local process crash via unchecked expression parsing
Published Dec 19, 2025 · Updated Dec 19, 2025
Out-of-bounds read in Binaryen 125 and earlier allows local users to crash wasm-opt by processing a malformed WebAssembly binary. WasmBinaryReader::readExpression reads input[pos] while seeking an expression terminator without first checking whether pos has reached the input buffer's end. Local users must invoke a Binaryen parser on a truncated data-segment expression; the demonstrated consequence is termination of that local process.
Summary
What happened
Out-of-bounds read in Binaryen 125 and earlier allows local users to crash wasm-opt by processing a malformed WebAssembly binary. WasmBinaryReader::readExpression reads input[pos] while seeking an expression terminator without first checking whether pos has reached the input buffer's end. Local users must invoke a Binaryen parser on a truncated data-segment expression; the demonstrated consequence is termination of that local process.
The record
- CVE
- CVE-2025-14956
- Published
- Dec 19, 2025
- Updated
- Dec 19, 2025
- Vendor
- WebAssembly
- Product
- Binaryen
- Classifications
- CWE-122, CWE-119, CWE-125, T1499
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Dec 19, 2025CVE publishedPublication date reported by the CVE source.
- Dec 19, 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=125
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
- Malformed WebAssembly data-segment reproducerproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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