Panic Risk in Wasmtime Due to Overlapping String Transcode
Summary
RUSTSEC-2026-0360: Overlapping string transcode in a fused adapter can panic. Affects wasmtime versions >= 49.0.0, < 49.0.3. Fixed in 49.0.3. How to fix ↓
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Background
Wasmtime is a high-performance runtime for WebAssembly, designed to execute WebAssembly modules efficiently and securely. It supports various features such as JIT compilation and AOT compilation, making it suitable for both server-side and client-side applications. However, a recent vulnerability has been identified that can lead to runtime panics under specific conditions, particularly when using a fused adapter for string transcoding.
Vulnerability Detail
The vulnerability arises from overlapping string transcode operations in a fused adapter, which can cause the application to panic. This issue is particularly concerning as it may lead to unexpected application crashes, potentially exposing sensitive data or disrupting service availability. The vulnerability was documented in the RustSec database and is linked to the Wasmtime security advisory, highlighting the need for immediate attention from developers using this package.
How To Fix
Latest published version: 50.0.0 as of 22 Oct 2026
Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
49.0.3
This is the first release that contains the fix.
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Workaround
As a temporary workaround, developers can avoid using the specific features of the fused adapter that lead to overlapping string transcoding until the package is updated. This may involve refactoring code to use alternative methods for string handling.
Conclusion
In summary, the overlapping string transcode vulnerability in Wasmtime poses a risk of application panics, which can disrupt services and expose sensitive data. It is crucial for developers to update to version 49.0.3 or later to mitigate this risk. Utilizing tools like Vulert can help monitor and alert for such vulnerabilities in real-time.
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FAQ
The CVSS score of this vulnerability is 5.9, indicating a moderate level of risk.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without any signup.
The potential consequences include application crashes and possible exposure of sensitive information, leading to service disruptions.
Yes, the vulnerability is fixed in Wasmtime version 49.0.3 and later.
If an immediate update is not possible, consider implementing workarounds by avoiding the use of the affected features until the package can be updated.
References
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