Description
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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| bytecodealliance | wasmtime | >= 29.0.0, < 36.0.5, >= 37.0.0, < 40.0.3, = 41.0.0 | — |
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.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | rust-wasmtime | 36.0.5+dfsg-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| 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 | — |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | rust | 1.75.0-25 | — |
Wolfi
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Wolfi rolling | wasmcloud | 2.0.1-r0 | — |
| Wolfi rolling | wizer | 10.0.0-r4 | — |
| Wolfi rolling | yara-x | 1.12.0-r1 | — |
| Wolfi rolling | zed | 0.228.0-r3 | — |
| Wolfi rolling | zellij | 0.44.0-r0 | — |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| crates.io | wasmtime | >= 29.0.0, < 36.0.5 | 36.0.5 | GHSA-vc8c-j3xm-xj73 |
| crates.io | wasmtime | >= 37.0.0, < 40.0.3 | 40.0.3 | GHSA-vc8c-j3xm-xj73 |
| crates.io | wasmtime | >= 41.0.0, < 41.0.1 | 41.0.1 | GHSA-vc8c-j3xm-xj73 |
| crates.io | wasmtime | >= 29.0.0, < 36.0.5 · >= 37.0.0, < 40.0.3 · >= 41.0.0, < 41.0.1 | 36.0.5, 40.0.3, 41.0.1 | RUSTSEC-2026-0006 |
References
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-vc8c-j3xm-xj73
- https://github.com/bytecodealliance/wasmtime/commit/728fa07184f8da2a046f48ef9b61f869dce133a6
- https://github.com/bytecodealliance/wasmtime/commit/799585fc362fcb991de147dd1a9f2ba0861ed440
- https://github.com/bytecodealliance/wasmtime/commit/ac92d9bb729ad3a6d93f0724c4c33a0c4a9c0227
- https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.memory_guard_size
- https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.signals_based_traps
- https://docs.wasmtime.dev/stability-release.html
- https://rustsec.org/advisories/RUSTSEC-2026-0006.html