Is This vulnerability exploited in the wild?

No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

How severe is This vulnerability?

Medium severity, with a CVSS score of 4, published 19 October 2026.

Which products and versions are affected?

Bytecode Alliance Wasmtime 46.0.0 to 48.0.6, 49.0.0 to 49.0.3; wasmtime (crates.io) SEMVER:introduced=46.0.0,fixed=48.0.7,introduced=49.0.0,fixed=49.0.4.

Is there a fix for This vulnerability?

Yes. wasmtime (crates.io): upgrade to 49.0.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is This vulnerability attacked?

It is attacked over the network.

Check whether you run Bytecode Alliance Wasmtime or wasmtime (crates.io) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Wasmtime panic lowering host-created component model stream

Severity: medium · CVSS 4 · Published 2026-10-19

Wasmtime is a WebAssembly runtime that allows applications to execute untrusted code safely. A flaw in how it converts data streams between host and guest code can cause the runtime to crash when a type mismatch occurs, leading to denial of service. An attacker with high privileges who can craft a malicious component model stream could trigger this crash.

Technologies: Bytecode Alliance Wasmtime, wasmtime (crates.io). Vendors: Bytecode Alliance, crates.io.

Quick answers

Is This vulnerability exploited in the wild?: No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
How severe is This vulnerability?: Medium severity, with a CVSS score of 4, published 19 October 2026.
Which products and versions are affected?: Bytecode Alliance Wasmtime 46.0.0 to 48.0.6, 49.0.0 to 49.0.3; wasmtime (crates.io) SEMVER:introduced=46.0.0,fixed=48.0.7,introduced=49.0.0,fixed=49.0.4.
Is there a fix for This vulnerability?: Yes. wasmtime (crates.io): upgrade to 49.0.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is This vulnerability attacked?: It is attacked over the network.
Am I affected?: Check whether you run Bytecode Alliance Wasmtime or wasmtime (crates.io) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

wasmtime (crates.io): upgrade to 49.0.4 or later
```
cargo update -p wasmtime
```

Technical details

The vulnerability exists in Wasmtime's component model stream lowering logic, where a host-created stream is passed to a guest expecting a different payload type. This type mismatch triggers a panic rather than graceful error handling. The attack requires network access, high privileges, and active user interaction to trigger; the impact is availability loss on the vulnerable system only.

Affected products

Bytecode Alliance wasmtime 46.0.0 to 48.0.6, 49.0.0 to 49.0.3

Identifiers

GHSA-9pvw-hwfg-92h5
RUSTSEC-2026-0378

Timeline

2026-10-19: disclosed
2026-10-20: advisory

References

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