CVE-2026-34944
Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64
Description
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, 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 disabled it's possible for out-of-sandbox data to be loaded, but this data is not visible to WebAssembly guests. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
INFO
Published Date :
April 9, 2026, 7:16 p.m.
Last Modified :
April 20, 2026, 6:27 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Wasmtime to a fixed version.
- Enable signals-based traps if possible.
- Ensure guard pages are enabled.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-34944.
| URL | Resource |
|---|---|
| https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-qqfj-4vcm-26hv | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-34944 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-34944
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-34944 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-34944 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Apr. 20, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions up to (excluding) 24.0.7 *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions from (including) 25.0.0 up to (excluding) 36.0.7 *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions from (including) 37.0.0 up to (excluding) 42.0.2 *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions from (including) 43.0.0 up to (excluding) 43.0.1 Added Reference Type GitHub, Inc.: https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-qqfj-4vcm-26hv Types: Vendor Advisory -
New CVE Received by [email protected]
Apr. 09, 2026
Action Type Old Value New Value Added Description Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, 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 disabled it's possible for out-of-sandbox data to be loaded, but this data is not visible to WebAssembly guests. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1. Added CVSS V4.0 AV:L/AC:L/AT:P/PR:L/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-248 Added Reference https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-qqfj-4vcm-26hv