CVE-2021-39216 Detail

Current Description

Wasmtime is an open source runtime for WebAssembly & WASI. In Wasmtime from version 0.19.0 and before version 0.30.0 there was a use-after-free bug when passing `externref`s from the host to guest Wasm content. To trigger the bug, you have to explicitly pass multiple `externref`s from the host to a Wasm instance at the same time, either by passing multiple `externref`s as arguments from host code to a Wasm function, or returning multiple `externref`s 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. The bug has been fixed, and users should upgrade to Wasmtime 0.30.0. 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`.


View Analysis Description

Severity



CVSS 3.x Severity and Metrics:

Nist CVSS score does not match with CNA score
CNA:  GitHub, Inc.
Base Score:  6.3 MEDIUM
Vector:  CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H


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Note: The CNA providing a score has achieved an Acceptance Level of Provider. The NVD will only audit a subset of scores provided by this CNA.

References to Advisories, Solutions, and Tools

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Hyperlink Resource
https://crates.io/crates/wasmtime Product 
https://github.com/bytecodealliance/wasmtime/commit/101998733b74624cbd348a2366d05760b40181f3 Third Party Advisory 
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-v4cp-h94r-m7xf Third Party Advisory 
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WAVBRYDDUIY2ZR3K3FO4BVYJKIMJ5TP7/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/Z2Z33FTXFQ6EOINVEQIP4DFBG53G5XIY/ Mailing List  Third Party Advisory 

Weakness Enumeration

CWE-ID CWE Name Source
CWE-416 Use After Free Provider acceptance level GitHub, Inc.  

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Change History

3 change records found show changes

Quick Info

CVE Dictionary Entry:
CVE-2021-39216
NVD Published Date:
09/17/2021
NVD Last Modified:
10/03/2021
Source:
GitHub, Inc.