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 14 October 2026.

Which products and versions are affected?

Bytecode Alliance Wasmtime 46.0.0 to 48.0.5, 49.0.0 to 49.0.2; wasmtime (crates.io) SEMVER:introduced=46.0.0,fixed=48.0.6,introduced=49.0.0,fixed=49.0.3.

Is there a fix for This vulnerability?

Yes. wasmtime (crates.io): upgrade to 49.0.3 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 out-of-bounds zero-length stream writes panic

Severity: medium · CVSS 4 · Published 2026-10-14

Wasmtime is a WebAssembly runtime that executes untrusted code. A flaw in stream write operations can cause the runtime to crash when processing certain zero-length writes, leading to denial of service of applications using Wasmtime to run WebAssembly modules.

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 14 October 2026.
Which products and versions are affected?: Bytecode Alliance Wasmtime 46.0.0 to 48.0.5, 49.0.0 to 49.0.2; wasmtime (crates.io) SEMVER:introduced=46.0.0,fixed=48.0.6,introduced=49.0.0,fixed=49.0.3.
Is there a fix for This vulnerability?: Yes. wasmtime (crates.io): upgrade to 49.0.3 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 49.0.3 or later
```
cargo update -p wasmtime
```

Technical details

An out-of-bounds memory access occurs during zero-length stream write operations in Wasmtime, triggered by insufficient bounds checking in the vulnerable code path. The vulnerability requires low privileges and passive user interaction (processing a malicious WebAssembly module). An attacker can crash the Wasmtime runtime, causing availability impact to the vulnerable system.

Affected products

Bytecode Alliance Wasmtime 46.0.0 to 48.0.5, 49.0.0 to 49.0.2

Identifiers

GHSA-93g3-36p8-x2gc
RUSTSEC-2026-0357

Timeline

2026-10-14: disclosed
2026-10-14: advisory

References

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