GHSA-9pvw-hwfg-92h5 - Wasmtime: Panic lowering a host-created component model stream into a guest that expects a different payload type
### Summary
Wasmtime may panic when the host lowers a component model `stream` or `future` into a guest, if the host created that stream or future with one payload type and the guest expects a different one. This can happen when an embedder creates a stream or future, passes it through a guest, receives it back under a type-erased type such as `StreamAny` or `FutureAny`, and then passes it to a guest function with a different payload type.
GHSA-63h4-6cx9-pjfj is a related advisory also fixing issues within this area, and this advisory is being issued for portions of Wasmtime that were not fixed as part of that advisory.
### Impact
This affects embedders that do all of the following:
1. Create streams or futures on the host with `StreamReader::new` or `FutureReader::new`
2. Pass them to guest code and receive them back as `StreamAny`, `FutureAny`, `Val::Stream`/`Val::Future`, or a typed reader whose payload is one of these.
3. Pass them on to a guest function whose `stream` or `future` payload type differs from the type the host created them with.
A guest can cause the mismatch in step 3 when it controls the types of the functions it exports or of the values it returns. In that case a malicious guest can make the host panic, a denial of service. Embedders that only use statically typed `StreamReader<T>`/`FutureReader<T>` with concrete payload types throughout, or that never pass streams or futures they created through a guest and back, are not affected.
MEDIUM
Severity & confidence
Source severitymedium
Platform severitymedium
Confidenceconfirmed
Exploitationunknown
CVSS-
Affected
VendorswasmtimeRed Hat
Productswasmtime
Reporting sources (3)
GitHub Security Advisories
Red Hat - CVE Feed
NIST NVD - National Vulnerability Database
Timeline & provenance
Published2026-10-23T22:04:45
Last updated2026-10-27T20:53:31
Ingested2026-10-23T22:19:50
FreshnessNEAR-REAL-TIME
Threat typeadvisory
Recommended action
Review the advisory and upgrade affected packages to the first patched version.
Next steps
- Identify affected systems in your environment.
- Apply the vendor patch or mitigation guidance.
- Review logs for indicators described in the advisory.
- Follow the affected vendor/product to track updates.
Confidence explanation
This object is reported by 3 independent sources.
Source type: vendor ยท Original: GitHub Security Advisories