EUVD-2026-21029

Wasmtime has use-after-free bug after cloning wasmtime::Linker...

Wasmtime has use-after-free bug after cloning `wasmtime::Linker`

Impact In version 43.0.0 of the wasmtime crate, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. The typical symptom of this...

GHSA-HFR4-7C6C-48W2 Wasmtime has use-after-free bug after cloning `wasmtime::Linker`

Impact In version 43.0.0 of the wasmtime crate, cloning a wasmtime::Linker is unsound and can result in use-after-free bugs. This bug is not controllable by guest Wasm programs. It can only be triggered by a specific sequence of embedder API calls made by the host. The typical symptom of this...

EUVD-2026-21027

Wasmtime: Miscompiled guest heap access enables sandbox escape on aarch64 Cranelift...

Wasmtime: Miscompiled guest heap access enables sandbox escape on aarch64 Cranelift

Impact Wasmtime's Cranelift compilation backend contains a bug on aarch64 when performing a certain shape of heap accesses which means that the wrong address is accessed. When combined with explicit bounds checks a guest WebAssembly module this can create a situation where there are two diverging...

GHSA-JHXM-H53P-JM7W Wasmtime: Miscompiled guest heap access enables sandbox escape on aarch64 Cranelift

Impact Wasmtime's Cranelift compilation backend contains a bug on aarch64 when performing a certain shape of heap accesses which means that the wrong address is accessed. When combined with explicit bounds checks a guest WebAssembly module this can create a situation where there are two diverging...

GHSA-Q49F-XG75-M9XW Wasmtime has host panic when Winch compiler executes `table.fill`

Impact 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 i...

EUVD-2026-21025

Wasmtime has host panic when Winch compiler executes table.fill...

Wasmtime has host panic when Winch compiler executes `table.fill`

Impact 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 i...

GHSA-M9W2-8782-2946 Wasmtime has host data leakage with 64-bit tables and Winch

Impact 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...

EUVD-2026-21024

Wasmtime has host data leakage with 64-bit tables and Winch...

Wasmtime has host data leakage with 64-bit tables and Winch

Impact 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...

EUVD-2026-21023

Wasmtime segfault or unused out-of-sandbox load with f64x2.splat operator on x86-64...

GHSA-QQFJ-4VCM-26HV Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64

On x86-64 platforms with SSE3 disabled Wasmtime's compilation of the f64x2.splat WebAssembly instruction with Cranelift may load 8 more bytes than is necessary. When signals-based-traps are disabled this can result in a uncaught segfault due to loading from unmapped guard pages. With guard pages...

Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64

On x86-64 platforms with SSE3 disabled Wasmtime's compilation of the f64x2.splat WebAssembly instruction with Cranelift may load 8 more bytes than is necessary. When signals-based-traps are disabled this can result in a uncaught segfault due to loading from unmapped guard pages. With guard pages...

EUVD-2026-21022

Wasmtime has a possible panic when lifting flags component value...

GHSA-M758-WJHJ-P3JQ Wasmtime has a possible panic when lifting `flags` component value

Impact Wasmtime contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This pani...

Wasmtime has a possible panic when lifting `flags` component value

Impact Wasmtime contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This pani...

EUVD-2026-20990

Wasmtime: Panic when transcoding misaligned utf-16 strings...

GHSA-JXHV-7H78-9775 Wasmtime: Panic when transcoding misaligned utf-16 strings

Impact 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 ...