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Vulnerability Details : 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`.
Publish Date : 2021-09-17 Last Update Date : 2021-10-04
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- CVSS Scores & Vulnerability Types

CVSS Score
3.3
Confidentiality Impact None (There is no impact to the confidentiality of the system.)
Integrity Impact Partial (Modification of some system files or information is possible, but the attacker does not have control over what can be modified, or the scope of what the attacker can affect is limited.)
Availability Impact Partial (There is reduced performance or interruptions in resource availability.)
Access Complexity Medium (The access conditions are somewhat specialized. Some preconditions must be satistified to exploit)
Authentication Not required (Authentication is not required to exploit the vulnerability.)
Gained Access None
Vulnerability Type(s) Bypass a restriction or similar
CWE ID 416

- Products Affected By CVE-2021-39216

# Product Type Vendor Product Version Update Edition Language
1 Application Bytecodealliance Wasmtime * * * * Version Details Vulnerabilities
2 OS Fedoraproject Fedora 35 * * * Version Details Vulnerabilities

- Number Of Affected Versions By Product

Vendor Product Vulnerable Versions
Bytecodealliance Wasmtime 1
Fedoraproject Fedora 1

- References For CVE-2021-39216

https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/Z2Z33FTXFQ6EOINVEQIP4DFBG53G5XIY/
FEDORA FEDORA-2021-68713440cb
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WAVBRYDDUIY2ZR3K3FO4BVYJKIMJ5TP7/
FEDORA FEDORA-2021-1805eacb48
https://crates.io/crates/wasmtime
https://github.com/bytecodealliance/wasmtime/commit/101998733b74624cbd348a2366d05760b40181f3
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-v4cp-h94r-m7xf CONFIRM

- Metasploit Modules Related To CVE-2021-39216

There are not any metasploit modules related to this CVE entry (Please visit www.metasploit.com for more information)


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