CVE-2026-8257Public exploit

Local crash via unchecked BrOn reference types

Published May 11, 2026 · Updated May 11, 2026

Reachable assertion in WebAssembly Binaryen 117 allows local users to crash wasm-ctor-eval with malformed WebAssembly input. IRBuilder::makeBrOn accepts non-reference ref or desc expressions, then finalize passes them to Type::getHeapType, whose isRef assertion aborts the process. Exploitation requires local execution of wasm-ctor-eval on a crafted module and interrupts only that tool process; no data disclosure or modification is reported.

CVSS severity5.5
Medium
EPSS probability0.16%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reachable assertion in WebAssembly Binaryen 117 allows local users to crash wasm-ctor-eval with malformed WebAssembly input. IRBuilder::makeBrOn accepts non-reference ref or desc expressions, then finalize passes them to Type::getHeapType, whose isRef assertion aborts the process. Exploitation requires local execution of wasm-ctor-eval on a crafted module and interrupts only that tool process; no data disclosure or modification is reported.

The record

CVE
CVE-2026-8257
Published
May 11, 2026
Updated
May 11, 2026
Vendor
WebAssembly
Product
Binaryen
Classifications
CWE-617, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 11, 2026CVE publishedPublication date reported by the CVE source.
  2. May 11, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=117

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

WebAssembly · Binaryenversion=117

Published CVSS scores

3.3VulDB CNACVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.8VulDB CNACVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P
3.3VulDB CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L/E:P/RL:O/RC:C
3.3VulDB CNACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
1.7VulDB CNAAV:L/AC:L/Au:S/C:N/I:N/A:P/E:POC/RL:OF/RC:C

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-617Reachable Assertion
T1499.004Application or System Exploitation Flood

Public exploit references

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Technologies

Your stack

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Your stack

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