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...

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...

EUVD-2026-21023

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

auto-wasi (=0.1.0), candid-extractor (>=0.1.0 <=0.1.2) +105 more potentially affected by CVE-2026-34944 via wasmtime (>=0.10.0 <=1.0.2)

wasmtime CARGO version =0.10.0, =0.1.0, =0.1.0, =0.1.0, =0.1.1, =0.5.3-0, =0.4.0, =0.4.0, =0.0.0, =0.5.0, =0.0.1-alpha, =0.40.1, =0.45.0, =0.1.0, =0.3.0 and more Source cves: CVE-2026-34944 Source advisory: OSV: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...

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...

EUVD-2026-21022

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

auto-wasi (=0.1.0), candid-extractor (>=0.1.0 <=0.1.2) +105 more potentially affected by CVE-2026-34943 via wasmtime (>=0.10.0 <=1.0.2)

wasmtime CARGO version =0.10.0, =0.1.0, =0.1.0, =0.1.0, =0.1.1, =0.5.3-0, =0.4.0, =0.4.0, =0.0.0, =0.5.0, =0.0.1-alpha, =0.40.1, =0.45.0, =0.1.0, =0.3.0 and more Source cves: CVE-2026-34943 Source advisory: OSV: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...

auto-wasi (=0.1.0), candid-extractor (>=0.1.0 <=0.1.2) +105 more potentially affected by CVE-2026-34942 via wasmtime (>=0.10.0 <=1.0.2)

wasmtime CARGO version =0.10.0, =0.1.0, =0.1.0, =0.1.0, =0.1.1, =0.5.3-0, =0.4.0, =0.4.0, =0.0.0, =0.5.0, =0.0.1-alpha, =0.40.1, =0.45.0, =0.1.0, =0.3.0 and more Source cves: CVE-2026-34942 Source advisory: OSV:GHSA-JXHV-7H78-9775...

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 ...

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 ...

GHSA-HX6P-XPX3-JVVV Wasmtime: Heap OOB read in component model UTF-16 to latin1+utf16 string transcoding

Summary Wasmtime contains a vulnerability where when transcoding a UTF-16 string to the latin1+utf16 component-model encoding it would incorrectly validate the byte length of the input string when performing a bounds check. Specifically the number of code units were checked instead of the byte...

auto-wasi (=0.1.0), candid-extractor (>=0.1.0 <=0.1.2) +105 more potentially affected by CVE-2026-34941 via wasmtime (>=0.10.0 <=1.0.2)

wasmtime CARGO version =0.10.0, =0.1.0, =0.1.0, =0.1.0, =0.1.1, =0.5.3-0, =0.4.0, =0.4.0, =0.0.0, =0.5.0, =0.0.1-alpha, =0.40.1, =0.45.0, =0.1.0, =0.3.0 and more Source cves: CVE-2026-34941 Source advisory: OSV:GHSA-HX6P-XPX3-JVVV...

EUVD-2026-20988

Wasmtime: Heap OOB read in component model UTF-16 to latin1+utf16 string transcoding...

Wasmtime: Heap OOB read in component model UTF-16 to latin1+utf16 string transcoding

Summary Wasmtime contains a vulnerability where when transcoding a UTF-16 string to the latin1+utf16 component-model encoding it would incorrectly validate the byte length of the input string when performing a bounds check. Specifically the number of code units were checked instead of the byte...

DEBIAN-CVE-2026-34987

Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch baseline non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch...