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Medium · 5.9 CVE-2026-34946 EUVD-2026-21025GHSA-q49f-xg75-m9xwRUSTSEC-2026-0089

Wasmtime's host panics when Winch compiler executes `table.fill`

Published Apr 9, 2026 · Updated Apr 9, 2026 · Assigned by GitHub_M

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 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.

Affected products

VendorProductAffectedFixed
bytecodealliance wasmtime >= 25.0.0, < 36.0.7, >= 37.0.0, < 42.0.2, >= 43.0.0, < 44.0.1 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
Debian 14 rust-wasmtime 36.0.7+dfsg-1 —
Debian 13 rust-wasmtime No fix yet —
ReleasePackageFixed inAdvisory
Ubuntu 26.10 rust-wasmtime No fix yet —
Ubuntu 26.04 LTS rust-wasmtime No fix yet —
Ubuntu 25.10 rust-wasmtime No fix yet —
Ubuntu 24.04 LTS rust-wasmtime No fix yet —

Wolfi

ReleasePackageFixed inAdvisory
Wolfi rolling wash No fix yet —
Wolfi rolling wasmcloud 2.0.4-r0 —
Wolfi rolling wizer 11.0.3-r10 —
Wolfi rolling yara-x 1.15.0-r2 —
Wolfi rolling zed 0.228.0-r3 —

Affected packages

EcosystemPackageAffectedFixedRecord
crates.io wasmtime >= 25.0.0, < 36.0.7 36.0.7 GHSA-q49f-xg75-m9xw
crates.io wasmtime >= 37.0.0, < 42.0.2 42.0.2 GHSA-q49f-xg75-m9xw
crates.io wasmtime >= 43.0.0, < 43.0.1 43.0.1 GHSA-q49f-xg75-m9xw
crates.io wasmtime >= 0.0.0-0, < 36.0.7 · >= 37.0.0, < 42.0.2 · >= 43.0.0, < 43.0.1 36.0.7, 42.0.2, 43.0.1 RUSTSEC-2026-0089

References