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fkie_cve-2026-24116

Wasmtime is a runtime for WebAssembly. Starting in version 29.0.0 and prior to version 36.0.5, 40.0.3, and 41.0.1, on x86-64 platforms with AVX, Wasmtime's compilation of the `f64.copysign` 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 disabled it's possible for out-of-sandbox data to be loaded, but unless there is another bug in Cranelift this data is not visible to WebAssembly guests. Wasmtime 36.0.5, 40.0.3, and 41.0.1 have been released to fix this issue. Users are recommended to upgrade to the patched versions of Wasmtime. Other affected versions are not patched and users should updated to supported major version instead. This bug can be worked around by enabling signals-based-traps. While disabling guard pages can be a quick fix in some situations, it's not recommended to disabled guard pages as it is a key defense-in-depth measure of Wasmtime.

GHSA-vc8c-j3xm-xj73 — Wasmtime segfault or unused out-of-sandbox load with f64.copysign operator on x86-64

Affected: crates.io: wasmtime

On x86-64 platforms with AVX Wasmtime's compilation of the `f64.copysign` 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 disabled it's possible for out-of-sandbox data to be loaded, but unless there is another bug in Cranelift this data is not visible to WebAssembly guests.

### Details

The `f64.copysign` operator, when operating on a value loaded from a memory (for example with `f64.load`), compiles with Cranelift to code on x86-64 with AVX that loads 128 bits (16 bytes) rather than the expected 64 bits (8 bytes) from memory. When the address is in-bounds for a (correct) 8-byte load but not an (incorrect) 16-byte load, this can load beyond memory by up to 8 bytes. This can result in three different behaviors depending on Wasmtime's configuration:

1. If guard pages are disabled then this extra data will be loaded. The extra data is present in the upper bits of a register, but the upper bits are not visible to WebAssembly guests. Actually witnessing this data would require a different bug in Cranelift, of which none are known. Thus in this situation while it's something we're patching in Cranelift it's not a security issue. 2. If guard pages are enabled, and [signals-based-traps] are enabled, then this operation will result in a safe WebAssembly trap. The trap is incorrect because the load is not out-of-bo…

RUSTSEC-2026-0006 — Wasmtime segfault or unused out-of-sandbox load with `f64.copysign` operator on x86-64

Affected: crates.io: wasmtime

This is an entry in the RustSec database for the Wasmtime security advisory located at https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-vc8c-j3xm-xj73 For more information see the GitHub-hosted security advisory.

UBUNTU-CVE-2026-24116

Affected: Ubuntu:24.04:LTS: rust-wasmtime, Ubuntu:25.10: rust-wasmtime, Ubuntu:26.04:LTS: rust-wasmtime