Out-of-bounds Read in Bytecodealliance Wasmtime
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.002 (14.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 14.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000
Affected products
- Bytecodealliance Wasmtime — versions >= 29.0.0, < 36.0.5, >= 37.0.0, < 40.0.3, = 41.0.0
Weakness classification (CWE)
References
- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-vc8c-j3xm-xj73 (Patch, Vendor Advisory)
- github.com/bytecodealliance/wasmtime/commit/728fa07184f8da2a046f48ef9b61f869dce… (Patch)
- github.com/bytecodealliance/wasmtime/commit/799585fc362fcb991de147dd1a9f2ba0861… (Patch)
- github.com/bytecodealliance/wasmtime/commit/ac92d9bb729ad3a6d93f0724c4c33a0c4a9… (Patch)
- docs.rs/wasmtime/latest/wasmtime/struct.Config.html (Product)
- docs.rs/wasmtime/latest/wasmtime/struct.Config.html (Product)
- docs.wasmtime.dev/stability-release.html (Release Notes)
- rustsec.org/advisories/RUSTSEC-2026-0006.html (Third Party Advisory)
Frequently asked questions
- What is CVE-2026-24116?
- CVE-2026-24116 is a medium-severity vulnerability in Bytecodealliance Wasmtime, classified under Out-of-bounds Read. CVSS score: 5.5/10. Published 2026-01-27.
- How severe is CVE-2026-24116?
- Medium severity. CVSS v3 base score is 5.5 out of 10.