CVE-2026-34987

Wasmtime (WebAssembly runtime) with the Winch baseline compiler backend on aarch64 is vulnerable. From 25.0.0 up to but not including 36.0.7, 42.0.2, and 43.0.1, using -Ccompiler=winch may allow a guest Wasm to access host memory outside the linear-memory sandbox. The aarch64 variant has an obser...

CVE-2026-44216

Wasmtime (WebAssembly runtime) contains a vulnerability in its allocation logic for WebAssembly tables: checked arithmetic may panic on overflow when allocating extremely large tables (possible with memory64). Affects Wasmtime versions 30.0.0–36.0.8, 43.0.2, and 44.0.1. The panic occurs during cr...

CVE-2026-34971

Wasmtime’s Cranelift backend on the aarch64 path contains a miscompile of a specific load pattern (load(iadd(base, ishl(index, amt)))) that can diverge between bounds checking and loading, enabling an arbitrary read/write of host memory and thus a sandbox escape for guest WebAssembly. Affected ra...

CVE-2026-34988

Summary: CVE-2026-34988 affects Wasmtime’s pooling allocator. In certain configurations, when embedding allows specific settings, memory contents can leak between linear memories across WebAssembly instances, breaking Wasmtime’s sandbox. The issue stems from incorrect VM-permission reset logic in...

CVE-2026-27572

Wasmtime (WebAssembly runtime) is affected by CVE-2026-27572 in the wasi:http/types.fields implementation. Prior to patched releases (Wasmtime 24.0.6, 36.0.6, 40.0.4, 41.0.4, and 42.0.0), the wasmtime-wasi-http crate uses a data structure that panics when the headers field set becomes excessively...

CVE-2026-34943

Wasmtime (WebAssembly runtime) has a vulnerability where lifting a flags-typed component-model value with Val can panic if bits outside the allowed flags set are present. Affected versions before fixes include 24.0.7, 36.0.7, 42.0.2, and 43.0.1; the panic occurs in Wasmtime’s Val lifting (not in ...

CVE-2026-34942

Wasmtime VM exposes a DoS risk due to a panic-triggering path when transcoding strings into utf16/latin1+utf16. Root cause: alignment verification for reallocated strings was improper, allowing unaligned pointers to be passed to the host by a malicious guest. Affected versions prior to fixed rele...

CVE-2026-27195

CVE-2026-27195 affects Wasmtime in versions where component-model-async is default (from 39.0.0). The bug causes a panic when a host embeds calls to wasmtime::component::[Typed]Func::call_async, drops the returned Future after polling, and then reuses the same component instance before the first ...

CVE-2026-34941

Wasmtime (WebAssembly runtime) contains a heap OOB read during transcoding of UTF-16 to the latin1+utf16 component-model encoding. The bug stems from validating the input length by code units instead of by byte length, causing reads beyond the WebAssembly linear memory during bounds checking. In ...

CVE-2026-27204

CVE-2026-27204 involves Wasmtime’s WASI host interfaces, where guest code could exhaust host resources due to insufficient limits on resource allocations. Affected versions prior to fixes include 24.0.6, 36.0.6, 40.0.4, 41.0.4, and 42.0.0. The fixes are released in Wasmtime 24.0.6, 36.0.6, 40.0.4...

CVE-2026-35195

The CVE-2026-35195 vulnerability affects Wasmtime (WebAssembly runtime) where the guest component’s realloc return value is not validated during transcoding of component-model strings. This can allow a guest to cause the host to write arbitrary transcoded string bytes to an arbitrary address up t...

CVE-2026-34945

Wasmtime (Winch) vulnerability: a bug in the 64-bit memory64 table.size translation could disclose data from the host stack to WebAssembly guests. Affected builds range 25.0.0 through just before 36.0.7, 42.0.2, and 43.0.1. Root cause: return value of table.size was statically typed as 32‑bit ins...

CVE-2026-34983

Wasmtime 43.0.0 contains a use-after-free bug when cloning wasmtime::Linker, triggered by a specific host embedder API sequence (clone, drop original, use cloned linker). The issue is not controllable by guest Wasm programs and can manifest as a segfault; it does not enable heap corruption or dat...

CVE-2026-47261

CVE-2026-47261 : Wasmtime-wasi WASI path_open(TRUNCATE) bypasses FilePerms::WRITE host restriction. Root cause: when OpenFlags::TRUNCATE is used, open_mode was not OR-ed with WRITE, allowing a READ-only preopen with DirPerms::all() to bypass access checks via wasip1 path_open or wasip2 descriptor...

CVE-2026-34946

Summary: Wasmtime’s Winch-based code path can panic the host when compiling the WebAssembly table.fill instruction. From 25.0.0 up to but not including 36.0.7, 42.0.2, and 43.0.1, a historical refactor changed how compiled code references table elements, but Winch paths were not updated, leading ...

CVE-2026-54786

Wasmtime’s native WASIp1 fd_renumber implementation leaks host resources because the guest-facing fd_renumber updates only the WASIp1 descriptor table, not the host’s underlying table. This affects wasm runtimes that expose fd_renumber and allow file descriptors; affected versions include all pri...

CVE-2026-35186

Wasmtime vulnerable due to a Winch backend bug in table.grow (affecting 32-bit tables) that could mis-interpret the result and allow reads/writes to the 16 bytes before linear memory, causing DoS and potential host-data leakage. Affected versions: Wasmtime 25.0.0 up to before 36.0.7, 42.0.2, and ...

CVE-2026-24116

CVE-2026-24116 affects Wasmtime (WebAssembly runtime) on x86-64 with AVX. The Cranelift-based compilation of the f64.copysign instruction may load 8 bytes too many, potentially causing an uncaught segfault when signals-based-traps are disabled and loading from guard pages occurs. Affected version...

CVE-2026-34944

Wasmtime (WebAssembly runtime) prior to versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1 on x86-64 with SSE3 disabled could compile f64x2.splat via Cranelift in a way that loads 8 extra bytes. When signals-based traps are disabled this may cause an uncaught segfault from unmapped guard pages. With gua...