Vulnerability in Bytecodealliance Wasmtime
CVE-2026-119135
Wasmtime 46.0.0 before 48.0.6 and 49.0.0 before 49.0.3 panics when the host reads a component model stream as a different Rust item type than it was created with, because the host-to-host read path asserts matching TypeIds instead of returning an error. Guest code can return a host-created StreamReader<U> that the embedder reads as StreamReader<T>, where both types map to the same component model type, crashing the embedding process.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-63h4-6cx9-pjfj (vendor-advisory)
- www.vulncheck.com/advisories/wasmtime-46.0.0-before-48.0.6-and-49.0.0-before-49… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-119135?
- CVE-2026-119135 is a medium-severity vulnerability in Bytecodealliance Wasmtime, classified under Reachable Assertion. CVSS score: 4.8/10. Published 2026-10-29.
- How severe is CVE-2026-119135?
- Medium severity. CVSS v3 base score is 4.8 out of 10.