# CVE-2026-126408: Wasmtime 47.0.0 before 48.0.8 Denial of Service via TypedFunc Type-Check Panic

Status: published. Published: 2026-11-13. Updated: 2026-11-13.

Wasmtime 47.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains an insufficient type-check in the TypedFunc embedder API for I31, Option<I31>, and Option<NoneRef> parameter or result types, reaching an unreachable!() path. A malicious guest module exporting a function that uses another anyref-hierarchy type can panic the host embedding, causing denial of service.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- bytecodealliance / wasmtime (wasmtime): ≥ 47.0.0; < 48.0.8 (affected, semver); 48.0.8 (unaffected, semver). Source: CNA: VulnCheck
- bytecodealliance / wasmtime (wasmtime): ≥ 49.0.0; < 49.0.5 (affected, semver); 49.0.5 (unaffected, semver). Source: CNA: VulnCheck
- bytecodealliance / wasmtime (wasmtime): ≥ 50.0.0; < 50.0.1 (affected, semver); 50.0.1 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 1 (low); CVSS:4.0/AV:A/AC:H/AT:P/PR:H/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 1.8 (low); CVSS:3.1/AV:A/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:L; source: CNA: VulnCheck

- CVSS 4.0: 1 (low); CVSS:4.0/AV:A/AC:H/AT:P/PR:H/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X; source: NVD: disclosure@vulncheck.com

- CVSS 3.1: 1.8 (low); CVSS:3.1/AV:A/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:L; source: NVD: disclosure@vulncheck.com

- CISA KEV: No listing in collected sources

- EPSS: 0.18% as of 2026-11-13; percentile 7.44%

- SSVC: exploitation poc; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-617

## Exploit evidence

- exploit: https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3982-jqvv-277m (ADP: CISA-ADP)

## References

- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3982-jqvv-277m (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/wasmtime-47.0.0-before-48.0.8-denial-of-service-via-typedfunc-type-check-panic (CNA: VulnCheck; third-party-advisory)

- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3982-jqvv-277m (ADP: CISA-ADP; exploit)

- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-3982-jqvv-277m (disclosure@vulncheck.com)

- https://www.vulncheck.com/advisories/wasmtime-47.0.0-before-48.0.8-denial-of-service-via-typedfunc-type-check-panic (disclosure@vulncheck.com)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-126408; retrieved 2026-11-13; source updated 2026-11-13

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126408; retrieved 2026-11-13; source updated 2026-11-13

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-126408; retrieved 2026-11-13; source updated Not reported

Revision: 41fa1613bdbef608b2a804970a7f0041397c5946a9e448fc055aeed7a3b8bb19

Canonical: https://y2.dev/cve/CVE-2026-126408

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