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

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2025-05-15 · updated 2026-06-17
Weakness: CWE-61

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.

Affected products

bytecodealliance wasm-micro-runtime: before 2.2.0 — fixed in 2.2.0

How to fix

Upgrade to a fixed version: bytecodealliance wasm-micro-runtime 2.2.0. Check the vendor advisory for mitigations.

References

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