CVE Vulnerability

CVE-2021-39216

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`.

3.3 /10

CVSS v2.0 :

V3 Legend

Vector :

Exploitability : 3.4 / Impact : 4.9

Attack Vector

Attack Complexity

Privileges Required

User Interaction

Confidentiality Impact NONE

Integrity Impact PARTIAL

Availability Impact PARTIAL

Scope

6.3 /10

CVSS v3.0 : MEDIUM

V3 Legend

Vector :

Exploitability : 1 / Impact : 5.2

Attack Vector LOCAL

Attack Complexity HIGH

Privileges Required LOW

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References
Link 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/Z2Z33FTXFQ6EOINVEQIP4DFBG53G5XIY/ Mailing List Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WAVBRYDDUIY2ZR3K3FO4BVYJKIMJ5TP7/ Mailing List Third Party Advisory
Configurations

Configuration 1

cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
Information

Published : 2021-09-17 08:15

Updated : 2021-12-21 02:18

NVD link : CVE-2021-39216

Mitre link : CVE-2021-39216

Products Affected
No products.
CWE
CWE-416