CVE-2025-43853 iwasm vulnerable to filesystem sandbox escape with symlink when using uvwasi feature

High 7.0 Published 15 May 2025 Updated 15 May 2025

Attackers can escape the filesystem sandbox via symlinks to read or create files on the host system when using the uvwasi feature on Windows.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: Not needed
Fix: None listed

What is CVE-2025-43853?

CVE-2025-43853 is a high-severity path traversal vulnerability in bytecodealliance wasm-micro-runtime, published on 15 May 2025. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

The WebAssembly Micro Runtime's (WAMR) iwasm package is the executable binary built with WAMR VMcore which supports WebAssembly System Interface (WASI) and command line interface. Anyone running WAMR up to and including version 2.2.0 or WAMR built with libc-uvwasi on Windows is affected by a symlink following vulnerability. On WAMR running in Windows, creating a symlink pointing outside of the preopened directory and subsequently opening it with create flag will create a file on host outside of the sandbox. If the symlink points to an existing host file, it's also possible to open it and read its content. Version 2.3.0 fixes the issue.

Weakness: CWE-61

Which versions are affected by CVE-2025-43853?

It affects 1 product.

Products include Bytecodealliance Webassembly Micro Runtime.

How do I fix CVE-2025-43853?

No fix has been published for CVE-2025-43853 yet. Limit exposure of the affected software until one is available.

Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.

Is CVE-2025-43853 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-43853 exists.

Sources

Also known as GHSA-8fc8-4g25-c8m7.