bytecodealliance wasmtime up to 24.0.6/36.0.6/42.0.1/44.0.0 out-of-bounds write

Summaryinfo

A vulnerability categorized as critical has been discovered in bytecodealliance wasmtime up to 24.0.6/36.0.6/42.0.1/44.0.0. This affects an unknown function. Such manipulation leads to out-of-bounds write. This vulnerability is uniquely identified as CVE-2026-35195. The attack can be launched remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in bytecodealliance wasmtime up to 24.0.6/36.0.6/42.0.1/44.0.0. Affected by this issue is an unknown functionality. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings between components contains a bug where the return value of a guest component's realloc is not validated before the host attempts to write through the pointer. This enables a guest to cause the host to write arbitrary transcoded string bytes to an arbitrary location up to 4GiB away from the base of linear memory. These writes on the host could hit unmapped memory or could corrupt host data structures depending on Wasmtime's configuration. Wasmtime by default reserves 4GiB of virtual memory for a guest's linear memory meaning that this bug will by default on hosts cause the host to hit unmapped memory and abort the process due to an unhandled fault. Wasmtime can be configured, however, to reserve less memory for a guest and to remove all guard pages, so some configurations of Wasmtime may lead to corruption of data outside of a guest's linear memory, such as host data structures or other guests's linear memories. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-35195 since 04/01/2026. The exploitation is known to be easy. The attack may be launched remotely. There are neither technical details nor an exploit publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 305829 (Linux Distros Unpatched Vulnerability : CVE-2026-35195), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 24.0.7, 36.0.7, 42.0.2 or 44.0.1 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (305829). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Productinfo

Vendor

• bytecodealliance

Name

• wasmtime

Version

• 24.0.0
• 24.0.1
• 24.0.2
• 24.0.3
• 24.0.4
• 24.0.5
• 24.0.6
• 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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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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