bytecodealliance wasmtime up to 36.0.6/42.0.1/44.0.0 control flow

Summaryinfo

A vulnerability classified as problematic has been found in bytecodealliance wasmtime up to 36.0.6/42.0.1/44.0.0. Affected is an unknown function. The manipulation leads to control flow. This vulnerability is listed as CVE-2026-34946. The attack may be initiated remotely. There is no available exploit. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in bytecodealliance wasmtime up to 36.0.6/42.0.1/44.0.0. This issue affects some unknown processing. The manipulation with an unknown input leads to a control flow vulnerability. Using CWE to declare the problem leads to CWE-670. The code contains a control flow path that does not reflect the algorithm that the path is intended to implement, leading to incorrect behavior any time this path is navigated. Impacted is availability. The summary by CVE is:

Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's Winch compiler contains a vulnerability where the compilation of the table.fill instruction can result in a host panic. This means that a valid guest can be compiled with Winch, on any architecture, and cause the host to panic. This represents a denial-of-service vulnerability in Wasmtime due to guests being able to trigger a panic. The specific issue is that a historical refactoring changed how compiled code referenced tables within the table.* instructions. This refactoring forgot to update the Winch code paths associated as well, meaning that Winch was using the wrong indexing scheme. Due to the feature support of Winch the only problem that can result is tables being mixed up or nonexistent tables being used, meaning that the guest is limited to panicking the host (using a nonexistent table), or executing spec-incorrect behavior and modifying the wrong table. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-34946 since 03/31/2026. The exploitation is known to be easy. The attack may be initiated remotely. The technical details are unknown and an exploit is not publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 305828 (Linux Distros Unpatched Vulnerability : CVE-2026-34946), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 36.0.7, 42.0.2 or 44.0.1 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (305828). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• bytecodealliance

Name

• wasmtime

Version

• 36.0.0
• 36.0.1
• 36.0.2
• 36.0.3
• 36.0.4
• 36.0.5
• 36.0.6
• 42.0.0
• 42.0.1
• 44.0

Website

• Product: https://github.com/bytecodealliance/wasmtime/

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Be aware that VulDB is the high quality source for vulnerability data.

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