Filesystem Sandbox Escape in wasmtime-wasi: Symlink Renaming Vulnerability
Summary
RUSTSEC-2026-0352: Filesystem sandbox escape when renaming symlinks with trailing slashes. Affects wasmtime-wasi across 3 version ranges.
>= 0.0.0-0, < 36.0.18
>= 37.0.0, < 48.0.6
>= 49.0.0, < 49.0.3
Fixed in 36.0.18, 48.0.6 or 49.0.3, depending on the release line you run. How to fix ↓
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Background
wasmtime-wasi is a Rust crate that provides a WebAssembly System Interface (WASI) for executing WebAssembly modules. It enables developers to run WebAssembly applications in a secure and isolated environment, ensuring that they do not have unrestricted access to the host system. However, this package is vulnerable to a filesystem sandbox escape when renaming symlinks with trailing slashes, which can lead to unauthorized access to the filesystem.
Vulnerability Detail
The vulnerability arises from improper handling of symlinks with trailing slashes in the wasmtime-wasi package. When a symlink is renamed with a trailing slash, it can escape the intended sandbox environment, allowing an attacker to manipulate the filesystem outside of the expected boundaries. This could lead to unauthorized access to sensitive files or directories, potentially compromising the integrity and confidentiality of the system. The vulnerability affects macOS and FreeBSD operating systems and has a CVSS score of 8.8, indicating a high severity level.
How To Fix
Latest published version: 50.0.0 as of 22 Oct 2026
Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
>= 0.0.0-0, < 36.0.1836.0.18 -
>= 37.0.0, < 48.0.648.0.6 -
>= 49.0.0, < 49.0.349.0.3
Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →
Workaround
As a temporary workaround, avoid using symlinks with trailing slashes in your applications that utilize the wasmtime-wasi package. Ensure that any symlink operations are performed without trailing slashes to mitigate the risk of sandbox escape.
Conclusion
The wasmtime-wasi package has a critical vulnerability that allows for filesystem sandbox escape through improper handling of symlinks with trailing slashes. It is essential to update to the patched versions to mitigate this risk and ensure the security of your applications.
See every vulnerability recorded for wasmtime-wasi →
FAQ
The vulnerability allows for a filesystem sandbox escape when renaming symlinks with trailing slashes, potentially exposing sensitive files.
Affected versions include all versions prior to 36.0.18, 37.0.0, and 48.0.6, as well as 49.0.0 before 49.0.3.
The vulnerability specifically affects macOS and FreeBSD operating systems.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in your software. Check your application against this vulnerability using the Vulert playground at Vulert Scanner.
The CVSS score of this vulnerability is 8.8, indicating a high severity level.
References
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