# Wasmtime unchecked memory usage in borrowed resource transfer

Source: https://junglewise.ai/threats/rustsec-2026-0424-unchecked-memory-usage-in-transferring-borrowed-b297503c  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-29. Updated: 2026-11-01  
License: CC BY 4.0 with a link back

Severity: info · Published 2026-10-29

Wasmtime is a runtime for executing WebAssembly code. A memory safety issue exists in how the runtime handles borrowed resources when transferring them between components, which could allow an attacker to cause memory corruption or other undefined behavior within a WebAssembly application.

Technologies: [Bytecode Alliance Wasmtime](https://junglewise.ai/threats/technologies/bytecode-alliance-wasmtime), [wasmtime (crates.io)](https://junglewise.ai/threats/technologies/wasmtime). Vendors: [Bytecode Alliance](https://junglewise.ai/threats/vendors/bytecode-alliance), [crates.io](https://junglewise.ai/threats/vendors/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?** Informational severity, published 29 October 2026.

**Which products and versions are affected?** Bytecode Alliance Wasmtime before 36.0.20; 37.0.0 before 48.0.8; 49.0.0 before 49.0.5; 50.0.0 before 50.0.1; wasmtime (crates.io) SEMVER:introduced=0.0.0-0,fixed=36.0.20,introduced=37.0.0,fixed=48.0.8,introduced=49.0.0,fixed=49.0.5,introduced=50.0.0,fixed=50.0.1.

**Is there a fix for This vulnerability?** Yes. wasmtime (crates.io): upgrade to 50.0.1 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 50.0.1 or later

  ```sh
  cargo update -p wasmtime
  ```


## Technical details

The vulnerability involves unchecked memory usage when transferring borrowed resources between components in Wasmtime. This is a memory safety issue that occurs during resource lifecycle management across component boundaries. The vulnerability affects multiple version ranges and has been patched in versions 36.0.20, 48.0.8, 49.0.5, and 50.0.1 or later.

## Affected products

- Bytecode Alliance Wasmtime before 36.0.20; 37.0.0 before 48.0.8; 49.0.0 before 49.0.5; 50.0.0 before 50.0.1

## Identifiers

- GHSA-6fr9-xmw9-5352
- RUSTSEC-2026-0424

## Timeline

- 2026-10-29: disclosed
- 2026-10-30: advisory

## References

- [https://crates.io/crates/wasmtime](https://crates.io/crates/wasmtime)
- [https://rustsec.org/advisories/RUSTSEC-2026-0424.html](https://rustsec.org/advisories/RUSTSEC-2026-0424.html)

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