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 2 October 2026.

Which products and versions are affected?

Bytecode Alliance Wasmtime 39.0.0 to 48.0.3, 49.0.0 to 49.0.1; wasmtime (crates.io) SEMVER:introduced=39.0.0,fixed=48.0.4,introduced=49.0.0,fixed=49.0.2.

Is there a fix for This vulnerability?

Yes. wasmtime (crates.io): upgrade to 49.0.2 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, in a software library.

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 component async-lifted callback stack buffer overflow

Severity: medium · CVSS 4 · Published 2026-10-02

Wasmtime is a WebAssembly runtime that executes sandboxed code. When processing async-lifted callbacks in WebAssembly components, the system fails to validate the number of result values, allowing an attacker to trigger a native stack buffer overflow. This can lead to code execution, data corruption, or system crashes.

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 2 October 2026.
Which products and versions are affected?: Bytecode Alliance Wasmtime 39.0.0 to 48.0.3, 49.0.0 to 49.0.1; wasmtime (crates.io) SEMVER:introduced=39.0.0,fixed=48.0.4,introduced=49.0.0,fixed=49.0.2.
Is there a fix for This vulnerability?: Yes. wasmtime (crates.io): upgrade to 49.0.2 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, in a software library.
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 49.0.2 or later
```
cargo update -p wasmtime
```

Technical details

The vulnerability exists in Wasmtime's component model implementation where async-lifted callback result counts are not validated before being used to write to the stack. An unauthenticated remote attacker can provide a malformed WebAssembly component over the network that triggers the unvalidated code path, causing a stack buffer overflow that enables arbitrary code execution or denial of service.

Affected products

Bytecode Alliance Wasmtime 39.0.0 to 48.0.3, 49.0.0 to 49.0.1

Identifiers

GHSA-32h6-97mm-8q3c
RUSTSEC-2026-0327

Timeline

2026-10-02: disclosed
2026-10-02: advisory

References

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