id: PYSEC-2021-322
details: Wasmtime is an open source runtime for WebAssembly & WASI. Wasmtime before
  version 0.30.0 is affected by a type confusion vulnerability. As a Rust library
  the `wasmtime` crate clearly marks which functions are safe and which are `unsafe`,
  guaranteeing that if consumers never use `unsafe` then it should not be possible
  to have memory unsafety issues in their embeddings of Wasmtime. An issue was discovered
  in the safe API of `Linker::func_*` APIs. These APIs were previously not sound when
  one `Engine` was used to create the `Linker` and then a different `Engine` was used
  to create a `Store` and then the `Linker` was used to instantiate a module into
  that `Store`. Cross-`Engine` usage of functions is not supported in Wasmtime and
  this can result in type confusion of function pointers, resulting in being able
  to safely call a function with the wrong type. Triggering this bug requires using
  at least two `Engine` values in an embedding and then additionally using two different
  values with a `Linker` (one at the creation time of the `Linker` and another when
  instantiating a module with the `Linker`). It's expected that usage of more-than-one
  `Engine` in an embedding is relatively rare since an `Engine` is intended to be
  a globally shared resource, so the expectation is that the impact of this issue
  is relatively small. The fix implemented is to change this behavior to `panic!()`
  in Rust instead of silently allowing it. Using different `Engine` instances with
  a `Linker` is a programmer bug that `wasmtime` catches at runtime. This bug has
  been patched and users should upgrade to Wasmtime version 0.30.0. If you cannot
  upgrade Wasmtime and are using more than one `Engine` in your embedding it's recommended
  to instead use only one `Engine` for the entire program if possible. An `Engine`
  is designed to be a globally shared resource that is suitable to have only one for
  the lifetime of an entire process. If using multiple `Engine`s is required then
  code should be audited to ensure that `Linker` is only used with one `Engine`.
affected:
- package:
    name: wasmtime
    ecosystem: PyPI
    purl: pkg:pypi/wasmtime
  ranges:
  - type: GIT
    repo: https://github.com/bytecodealliance/wasmtime
    events:
    - introduced: "0"
    - fixed: b39f087414f27ae40c44449ed5d1154e03449bff
  - type: ECOSYSTEM
    events:
    - introduced: "0"
    - fixed: 0.30.0
  versions:
  - 0.0.1
  - 0.0.2
  - 0.11.0
  - 0.12.0
  - 0.15.0
  - 0.15.1
  - 0.16.0
  - 0.16.1
  - 0.17.0
  - 0.18.0
  - 0.18.1
  - 0.18.2
  - 0.19.0
  - 0.20.0
  - 0.21.0
  - 0.22.0
  - 0.23.0
  - 0.24.0
  - 0.25.0
  - 0.26.0
  - 0.27.0
  - 0.28.0
  - 0.28.1
  - 0.29.0
  - 0.9.0
references:
- type: WEB
  url: https://crates.io/crates/wasmtime
- type: FIX
  url: https://github.com/bytecodealliance/wasmtime/commit/b39f087414f27ae40c44449ed5d1154e03449bff
- type: ADVISORY
  url: https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-q879-9g95-56mx
aliases:
- CVE-2021-39219
- GHSA-q879-9g95-56mx
modified: "2021-09-17T22:30:49.947373Z"
published: "2021-09-17T20:15:00Z"