What is the CVSS score of CVE-2021-39216?

CVE-2021-39216 has a CVSS 3.1 base score of 6.3 (Medium). CVSS vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H. EPSS exploitation probability: 0.3%.

Is there a patch available for CVE-2021-39216?

Yes, a patch is available for CVE-2021-39216. Update the affected software to the latest version immediately.

Wasmtime CVE-2021-39216

MEDIUM

Use After Free (CWE-416)

2021-09-17 security-advisories@github.com

Use After Free Memory Corruption Information Disclosure Wasmtime Fedora

6.3

CVSS 3.1 · Vendor: github

Severity by source

Vendor (github) PRIMARY

6.3 MEDIUM

AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H

Primary rating from Vendor (github) · only source for this CVE.

CVSS VectorVendor: github

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H

Attack Vector

Local

Attack Complexity

High

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

High

Lifecycle Timeline

CVE Published

Sep 17, 2021 - 20:15 cve.org

MEDIUM 6.3

Blast Radius

ecosystem impact

† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth

15 cargo packages depend on wasmtime (14 direct, 1 indirect)
17 pypi packages depend on wasmtime (7 direct, 10 indirect)

Ecosystem-wide dependent count for version 0.30.0 and other introduced versions.

DescriptionCVE.org

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 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. 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.

AnalysisAI

Wasmtime is an open source runtime for WebAssembly & WASI. Rated medium severity (CVSS 6.3). No vendor patch available.

Technical ContextAI

This vulnerability is classified as Use After Free (CWE-416), which allows attackers to access freed memory to execute arbitrary code or crash the application. 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 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. 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. Affected products include: Bytecodealliance Wasmtime, Fedoraproject Fedora. Version information: version 0.19.0.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Use smart pointers or garbage-collected languages. Set pointers to NULL after freeing. Enable memory sanitizers.