What is CVE-2026-8257?

CVE-2026-8257 is a low-severity vulnerability in Webassembly Binaryen, classified under Reachable Assertion. CVSS score: 3.3/10. Published 2026-05-11.

How severe is CVE-2026-8257?

Low severity. CVSS v3 base score is 3.3 out of 10.

Vulnerability in Webassembly Binaryen

CVE-2026-8257

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.

Published 2026-05-11 · last modified 2026-07-23.

CVSS v3 metric

CVSS v3 base score 3.3 (Low). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.002 (7.7th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 8th percentile — 7.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000

Affected products

Webassembly Binaryen — versions 117

Weakness classification (CWE)

CWE-617 — Reachable Assertion

References

vuldb.com/vuln/362554 (technical-description, VDB Entry, Third Party Advisory, vdb-entry)
vuldb.com/vuln/362554/cti (signature, Permissions Required, permissions-required, VDB Entry)
vuldb.com/submit/809552 (VDB Entry, Third Party Advisory, third-party-advisory)
github.com/WebAssembly/binaryen/issues/8633 (issue-tracking, Exploit, Third Party Advisory, Issue Tracking)
github.com/WebAssembly/binaryen/pull/8635 (issue-tracking, Patch, Mitigation, patch)
github.com/HackC0der/CVE-Repos/blob/main/wasm-binaryen/Assertion_Failure_isRef_… (Exploit, exploit, patch)
github.com/WebAssembly/binaryen/commit/1251efbc1ea471c1311d2726b2bbe061ff2a291c (Patch, patch)
github.com/WebAssembly/binaryen/ (Product, product)

Frequently asked questions

What is CVE-2026-8257?: CVE-2026-8257 is a low-severity vulnerability in Webassembly Binaryen, classified under Reachable Assertion. CVSS score: 3.3/10. Published 2026-05-11.
How severe is CVE-2026-8257?: Low severity. CVSS v3 base score is 3.3 out of 10.