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.
CVE-2026-8257
“—” beside the score: it is equal to NVD's CVSS score.
This medium-severity CVE scores 5.5 under NVD CVSS v3. EPSS exploit probability: 0.2% (5th percentile of EPSS-scored CVEs). GitHub Security Advisory CVSS 3.3 is lower than this score; a lower GitHub score revises it only when its advisory is newer than the CVE record's last change, and this advisory (published 2026-05-11) is not newer than that change (2026-07-23), so it does not.
Also known asEUVD-2026-29013 (ENISA EUVD) · GHSA-gmmj-chcc-2f2x (GitHub Security Advisories)Source: ENISA EUVD
- CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
An upstream fix is merged but not yet released — mitigate (WAF / firewall / segmentation) until the release ships, then apply it.
- CVSS v3
- 5.5
- EG Score
- 5.5MEDIUMmedium confidence
- EG Risk
- 41EG Risk 41/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity55% × 45%Impact severity (EG Severity): CVSS 5.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation40% × 40%EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines until it ships, then apply the release. - EPSS PROB
- 0.2%
- EPSS %ILE
- 5th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS. FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
An upstream fix is merged but not yet in a tagged release. Restrict network exposure of the affected system or apply the vendor's mitigation within your standard update timelines until it ships, then apply the release.
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
May 11, 2026
Last Modified
July 23, 2026
Advisory Details (5)
Auto-updated Jul 25, 2026Avoid assertion in BrOn parsing
Fix merged in WebAssembly/binaryen PR #8635 on 2026-04-21 — awaiting tagged release
https://github.com/WebAssembly/binaryen/pull/8635Assertion failure isRef() in wasm::Type::getHeapType() at wasm-type.h:407 (main branch @3ef8d19) · Issue #8633 · WebAssembly/binaryen · GitHub
https://github.com/WebAssembly/binaryen/issues/8633commit 1251efbc1ea4 (WebAssembly/binaryen)
Fix landed in WebAssembly/binaryen commit 1251efbc1ea4 — awaiting tagged release
https://github.com/WebAssembly/binaryen/commit/1251efbc1ea471c1311d2726b2bbe061ff2a291cGitHub - WebAssembly/binaryen: Optimizer and compiler/toolchain library for WebAssembly · GitHub
https://github.com/WebAssembly/binaryen/CVE-Repos/wasm-binaryen/Assertion_Failure_isRef_wasm_Type_getHeapType_commit_3ef8d19 at main · HackC0der/CVE-Repos · GitHub
https://github.com/HackC0der/CVE-Repos/blob/main/wasm-binaryen/Assertion_Failure_isRef_wasm_Type_getHeapType_commit_3ef8d19Affected Packages
(4 across 4 ecosystems)
Debian:11(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| binaryen | 100-1 ... 99-3 (24 versions) |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| binaryen | 108-1 ... 131-2 (16 versions) |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| binaryen | 120-4 ... 131-2 (10 versions) |
| — |
Debian:14(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| binaryen | 120-4 ... 131-2 (10 versions) |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 36× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 96 of 210 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. 4 repeat rows among the latest 100 are merged into the row they repeat. The 114 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-10-30 01:25 UTCOSV refresh
- 2026-10-29 16:34 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-10-28 16:33 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-10-26 16:32 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-10-25 16:34 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-10-25 13:57 UTCEG score recompute
- 2026-10-24 16:34 UTCEPSS rescoreEPSS 0.2% · 8th percentile
- 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.2% · 8th percentile
- 2026-10-22 16:35 UTCEPSS rescoreEPSS 0.2% · 8th percentile
- 2026-10-22 13:43 UTCEG score recompute
- 2026-10-22 13:43 UTCGHSA enrichmentGHSA-gmmj-chcc-2f2x · GitHub severity LOW · GitHub CVSS 3.3
- 2026-10-21 16:34 UTCEPSS rescoreEPSS 0.2% · 8th percentile
- 2026-10-20 16:34 UTCEPSS rescoreEPSS 0.2% · 8th percentile
- 2026-10-19 16:33 UTCEPSS rescoreEPSS 0.2% · 8th percentile
- 2026-10-18 16:33 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-18 03:08 UTCEG score recompute
- 2026-10-17 16:35 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-16 16:44 UTCEPSS rescoreEPSS 0.2% · 8th percentile
- 2026-10-15 16:33 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-14 16:34 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-13 16:35 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-12 16:35 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-12 14:55 UTCEG score recompute
- 2026-10-11 19:19 UTCEG score recompute
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- 2026-10-11 16:36 UTCEG score recompute
- 2026-10-11 13:54 UTCEG score recompute
- 2026-10-11 13:50 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-08 17:13 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-06 15:18 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-05 17:44 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-10-01 19:51 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-09-30 15:04 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-09-30 06:58 UTCOSV refresh
- 2026-09-28 13:52 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-09-27 13:49 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-09-26 15:59 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-09-24 14:04 UTCEPSS rescoreEPSS 0.2% · 7th percentile
- 2026-09-23 17:54 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-22 16:01 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-21 21:09 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-20 20:16 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-17 19:32 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-16 14:09 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-15 03:12 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-13 16:48 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-12 15:02 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-11 12:23 UTCOSV refresh
- 2026-09-08 22:01 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-06 13:48 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-05 15:31 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-04 05:07 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-09-01 04:40 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-28 21:42 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-26 14:47 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-24 14:18 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-23 18:44 UTCEG score recompute
- 2026-08-23 18:44 UTCGHSA enrichmentGHSA-gmmj-chcc-2f2x · GitHub severity LOW · GitHub CVSS 3.3
- 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-20 22:56 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-19 17:04 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-18 13:49 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-17 11:19 UTCEG score recompute
- 2026-08-17 11:19 UTCGHSA enrichmentGHSA-gmmj-chcc-2f2x · GitHub severity LOW · GitHub CVSS 3.3
- 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-16 04:28 UTCEG score recompute
- 2026-08-16 04:28 UTCGHSA enrichmentGHSA-gmmj-chcc-2f2x · GitHub severity LOW · GitHub CVSS 3.3
- 2026-08-16 02:15 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-15 01:31 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-14 03:02 UTCEG score recompute
- 2026-08-14 03:02 UTCGHSA enrichmentGHSA-gmmj-chcc-2f2x · GitHub severity LOW · GitHub CVSS 3.3
- 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-13 01:38 UTCEG score recompute
- 2026-08-13 01:38 UTCGHSA enrichmentGHSA-gmmj-chcc-2f2x · GitHub severity LOW · GitHub CVSS 3.3
- 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-12 01:48 UTCGHSA enrichmentGHSA-gmmj-chcc-2f2x · GitHub severity LOW · GitHub CVSS 3.3
- 2026-08-11 01:58 UTCEG score recompute
- 2026-08-11 01:58 UTCGHSA enrichmentGHSA-gmmj-chcc-2f2x · GitHub severity LOW · GitHub CVSS 3.3
- 2026-08-11 00:00 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-10 02:08 UTCEG score recompute
- 2026-08-10 02:08 UTCGHSA enrichmentGHSA-gmmj-chcc-2f2x · GitHub severity LOW · GitHub CVSS 3.3
- 2026-08-09 13:47 UTCEPSS rescoreEPSS 0.2% · 5th percentile
- 2026-08-09 02:18 UTCEG score recompute
Related CVEs(same product + same CWE)
Same product
10 shownDebian:11:binaryen
Frequently asked(5)
What is CVE-2026-8257?
When was the CVE record for CVE-2026-8257 published?
Is CVE-2026-8257 actively exploited?
What is the CVSS score of CVE-2026-8257?
How do I remediate CVE-2026-8257?
Dependency Blast Radius
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