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CVE-2026-34945 Details

Description

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 bug where a 64-bit table, part of the memory64 proposal of WebAssembly, incorrectly translated the table.size instruction. This bug could lead to disclosing data on the host's stack to WebAssembly guests. The host's stack can possibly contain sensitive data related to other host-originating operations which is not intended to be disclosed to guests. This bug specifically arose from a mistake where the return value of table.size was statically typed as a 32-bit integer, as opposed to consulting the table's index type to see how large the returned register could be. When combined with details about Wnich's ABI, such as multi-value returns, this can be combined to read stack data from the host, within a guest. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:6.5 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-m9w2-8782-2946	[email protected]	Vendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-681	Incorrect Conversion between Numeric Types	[email protected]

Affected Products

Product	Versions
bytecodealliance wasmtime	>= 25.0.0, < 36.0.7 >= 37.0.0, < 42.0.2 >= 43.0.0, < 43.0.1
CPE cpe:2.3:a:bytecodealliance:wasmtime::::::rust::* Remediation No remediation found in references.

Change History

4 change records found show changes

Date	Action	Recorded By
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
Apr 20, 2026	Initial Analysis	[email protected]
Apr 9, 2026	New CVE Received	[email protected]