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OpenAdvisories
Medium · 5.9 CVE-2026-34942 EUVD-2026-20990GHSA-jxhv-7h78-9775RUSTSEC-2026-0092

Wasmtime panics when transcoding misaligned utf-16 strings

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

Description

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 into the Component Model's utf16 or latin1+utf16 encodings improperly verified the alignment of reallocated strings. This meant that unaligned pointers could be passed to the host for transcoding which would trigger a host panic. This panic is possible to trigger from malicious guests which transfer very specific strings across components with specific addresses. Host panics are considered a DoS vector in Wasmtime as the panic conditions are controlled by the guest in this situation. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.

Affected products

VendorProductAffectedFixed
bytecodealliance wasmtime < 24.0.7, >= 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 —
ReleasePackageFixed inAdvisory
openSUSE Tumbleweed zed 1.24.2-1.1 openSUSE-SU-2026:12355-1

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 < 24.0.7 24.0.7 GHSA-jxhv-7h78-9775
crates.io wasmtime >= 25.0.0, < 36.0.7 36.0.7 GHSA-jxhv-7h78-9775
crates.io wasmtime >= 37.0.0, < 42.0.2 42.0.2 GHSA-jxhv-7h78-9775
crates.io wasmtime >= 43.0.0, < 43.0.1 43.0.1 GHSA-jxhv-7h78-9775
crates.io wasmtime >= 0.0.0-0, < 24.0.7 · >= 25.0.0, < 36.0.7 · >= 37.0.0, < 42.0.2 · >= 43.0.0, < 43.0.1 24.0.7, 36.0.7, 42.0.2, 43.0.1 RUSTSEC-2026-0092

Advisories 1

References