Wasmtime is a runtime for WebAssembly. Prior to 36.0.19 and 43.0.0, the Cranelift compiler backend bit-packs SSA value indices in a way that can silently overflow in release builds when compiling a sufficiently large or specially crafted Wasm function with many SSA values. The overflow can make Cranelift reference incorrect IR values, causing arbitrary miscompilation, type confusion, and other attacker-controlled effects that may escape the Wasm sandbox on any architecture using the default Cranelift backend. This issue is fixed in versions 36.0.19 and 43.0.0.
CVE-2026-115889
CRITICALPre-NVD 9.99.9Trending — 3 sources updated this week
EchelonGraph scoreMEDIUM confidence
“—” beside the score: it is equal to the CVSS score beside it.
This critical-severity CVE scores 9.9 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.5% (39th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.
Triggered by: Headline CVSS from a secondary CVSS source
Sources: EPSS, a secondary CVSS source
Also known asEUVD-2026-109186 (ENISA EUVD) · GHSA-897f-g5gm-fmxm (GitHub Security Advisories)Source: ENISA EUVD
9.9EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0.5%CVSS: 9.9Exploit: None knownExposed services: Not assessed
A fix is available — apply it.
- CVSS v3
- 9.9
- EG Score
- 9.9CRITICALmedium confidence
- EG Risk
- 45EG Risk 45/100
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)Severity99% × 45%Impact severity (EG Severity): CVSS 9.9 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.4% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.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 none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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: A fix is available. Apply it within your standard update timelines. - EPSS PROB
- 0.5%
- EPSS %ILE
- 39th
- 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 (9.9): severity, escalated by confirmed exploitation. This CVE's 9.9 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.9 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.a secondary CVSS source · CVSS v3.0 or v3.1
- EG Likelihood
- 0.5% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-26). 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: 14 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).
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (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)14 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 total (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
October 23, 2026
Last Modified
October 26, 2026
Advisory Details (7)
Auto-updated Oct 26, 2026Patch available. Sources: github_commit, github_pr, github_release, github.
GitHub advisoryMentions a patch (unverified)
Bit-packing in Cranelift compiler causes silent overflow and miscompilation · Advisory · bytecodealliance/wasmtime · GitHub
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-897f-g5gm-fmxmGitHub release Patch Available
Release v43.0.0 (bytecodealliance/wasmtime)
Patch available: bytecodealliance/wasmtime v43.0.0
https://github.com/bytecodealliance/wasmtime/releases/tag/v43.0.0GitHub release Patch Available
Release v36.0.19 (bytecodealliance/wasmtime)
Patch available: bytecodealliance/wasmtime v36.0.19
https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.19GitHub pull request
Security fixes for release 36.0.19
Fix merged in bytecodealliance/wasmtime PR #14818 on 2026-10-19 — awaiting tagged release
https://github.com/bytecodealliance/wasmtime/pull/14818GitHub pull request
Cranelift: update ValueDataPacked to support full Value range.
Fix merged in bytecodealliance/wasmtime PR #12613 on 2026-02-18 — awaiting tagged release
https://github.com/bytecodealliance/wasmtime/pull/12613GitHub commit
commit f517bd6e890c (bytecodealliance/wasmtime)
Fix landed in bytecodealliance/wasmtime commit f517bd6e890c — awaiting tagged release
https://github.com/bytecodealliance/wasmtime/commit/f517bd6e890c7c1291ab9fe05d8cc0c9f11e56aaGitHub commit
commit ba8f7d70caa1 (bytecodealliance/wasmtime)
Fix landed in bytecodealliance/wasmtime commit ba8f7d70caa1 — awaiting tagged release
https://github.com/bytecodealliance/wasmtime/commit/ba8f7d70caa1825b7f64fa75cd9d03f4a438dae0Vendor Advisories for CVE-2026-115889(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Affected Packages
(1 across 1 ecosystem)
crates.io(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| wasmtime | — |
| — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 11× in last 7d / 11× 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.
- 2026-10-26 18:30 UTCEG score recompute
- 2026-10-26 17:47 UTCEG score recompute
- 2026-10-26 16:30 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-10-25 22:23 UTCEG score recompute
- 2026-10-25 16:32 UTCEPSS rescoreEPSS 0.5% · 39th percentile
- 2026-10-25 14:50 UTCEG score recompute
- 2026-10-24 22:25 UTCEG score recompute
- 2026-10-24 16:32 UTCEPSS rescoreEPSS 0.7% · 51st percentile
- 2026-10-23 22:28 UTCEG score recompute
- 2026-10-23 21:35 UTCEG score recomputeFirst assessed: 9.9 CRITICAL
- 2026-10-23 21:34 UTCMITRE cvelistV5first tracked
Related CVEs(same product + same CWE)
Same product
10 showncrates.io:wasmtime
Frequently asked(5)
What is CVE-2026-115889?
CVE-2026-115889 is a critical-severity vulnerability; its CVE record was published on October 23, 2026. Wasmtime is a runtime for WebAssembly. Prior to 36.0.19 and 43.0.0, the Cranelift compiler backend bit-packs SSA value indices in a way that can silently overflow in release builds when compiling a sufficiently large or specially crafted Wasm function with many SSA values. The overflow can make…
When was the CVE record for CVE-2026-115889 published?
The CVE record for CVE-2026-115889 was published on October 23, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 26, 2026; the record at its source may have been updated since.
Is CVE-2026-115889 actively exploited?
CVE-2026-115889 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.5% probability of exploitation in the next 30 days (39th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-115889?
CVE-2026-115889 has a CVSS base score of 9.9 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-115889?
A fix for CVE-2026-115889 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-115889 are linked in the Vendor Advisories panel on this page.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-115889
Is Your Infrastructure Affected by CVE-2026-115889?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.