GHSA-v4cp-h94r-m7xf

Suggest an improvement
Source
https://github.com/advisories/GHSA-v4cp-h94r-m7xf
Import Source
https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/09/GHSA-v4cp-h94r-m7xf/GHSA-v4cp-h94r-m7xf.json
JSON Data
https://api.osv.dev/v1/vulns/GHSA-v4cp-h94r-m7xf
Aliases
Published
2021-09-20T19:54:05Z
Modified
2024-11-19T18:23:24.646607Z
Severity
  • 6.3 (Medium) CVSS_V3 - CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H CVSS Calculator
  • 6.1 (Medium) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N CVSS Calculator
Summary
Use after free passing `externref`s to Wasm in Wasmtime
Details

Impact

There was a use-after-free bug when passing externrefs from the host to guest Wasm content.

To trigger the bug, you have to explicitly pass multiple externrefs from the host to a Wasm instance at the same time, either by

  • passing multiple externrefs as arguments from host code to a Wasm function,
  • or returning multiple externrefs to Wasm from a multi-value return function defined in the host.

If you do not have host code that matches one of these shapes, then you are not impacted.

If Wasmtime's VMExternRefActivationsTable became filled to capacity after passing the first externref in, then passing in the second externref could trigger a garbage collection. However the first externref is not rooted until we pass control to Wasm, and therefore could be reclaimed by the collector if nothing else was holding a reference to it or otherwise keeping it alive. Then, when control was passed to Wasm after the garbage collection, Wasm could use the first externref, which at this point has already been freed.

We have reason to believe that the effective impact of this bug is relatively small because usage of externref is currently quite rare.

Patches

The bug has been fixed, and users should upgrade to Wasmtime 0.30.0.

Additionally, we have updated our primary externref fuzz target such that it better exercises these code paths and we can have greater confidence in their correctness going forward.

Workarounds

If you cannot upgrade Wasmtime yet, you can avoid the bug by disabling reference types support in Wasmtime by passing false to wasmtime::Config::wasm_reference_types.

References

For more information

If you have any questions or comments about this advisory:

Database specific
{
    "nvd_published_at": "2021-09-17T20:15:00Z",
    "cwe_ids": [
        "CWE-416"
    ],
    "severity": "MODERATE",
    "github_reviewed": true,
    "github_reviewed_at": "2021-09-17T20:05:21Z"
}
References

Affected packages

crates.io / wasmtime

Package

Affected ranges

Type
SEMVER
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
0.30.0

PyPI / wasmtime

Package

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected
Fixed
0.30.0

Affected versions

0.*

0.0.1
0.0.2
0.9.0
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