Medium severity · published May 11, 2026
CVE-2026-8257
WebAssembly Binaryen BrOn wasm-ir-builder.cpp makeBrOn assertion
5.5
CVSS
0.2%
EPSS
No
On KEV
Description
A vulnerability was detected in WebAssembly Binaryen up to 117. This issue affects the function IRBuilder::makeBrOn of the file src/wasm/wasm-ir-builder.cpp of the component BrOn Parser. Performing a manipulation results in reachable assertion. The attack needs to be approached locally. The exploit is now public and may be used. The patch is named 1251efbc1ea471c1311d2726b2bbe061ff2a291c. It is suggested to install a patch to address this issue.
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 5% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
BI
Binaryen · WebAssembly
117 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-8257
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-8257
Exploit
https://github.com/HackC0der/CVE-Repos/blob/main/wasm-binaryen/Assertion_Failure_isRef_wasm_Type_getHeapType_commit_3ef8d19
Product
https://github.com/WebAssembly/binaryen/
Patch
https://github.com/WebAssembly/binaryen/commit/1251efbc1ea471c1311d2726b2bbe061ff2a291c
Exploit
https://github.com/WebAssembly/binaryen/issues/8633
Mitigation
https://github.com/WebAssembly/binaryen/pull/8635
Third Party Advisory
https://vuldb.com/submit/809552
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