CVE-2026-34944: CWE-248: Uncaught Exception in bytecodealliance wasmtime
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.
AI Analysis
Technical Summary
Wasmtime, a WebAssembly runtime by bytecodealliance, has a vulnerability (CVE-2026-34944) related to its compilation of the f64x2.splat instruction on x86-64 systems with SSE3 disabled. The Cranelift compiler may load 8 extra bytes beyond what is necessary. If signals-based traps are disabled, this leads to an uncaught segmentation fault due to loading from unmapped guard pages. If guard pages are disabled, out-of-sandbox data could be loaded, but this data remains inaccessible to WebAssembly guests. This vulnerability is fixed in wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Potential Impact
The vulnerability can cause an uncaught segmentation fault, potentially leading to runtime crashes. In configurations where guard pages are disabled, it may allow loading of out-of-sandbox data, though this data is not visible to WebAssembly guests, limiting the impact. There are no known reports of exploitation in the wild. The CVSS 4.1 score reflects a medium severity with local attack vector and partial user interaction required.
Mitigation Recommendations
A fix is available in wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1. Users should upgrade to one of these versions to remediate the vulnerability. Since the vendor advisory indicates these versions contain the fix, applying the official update is the recommended mitigation. No additional mitigations are specified or required.
CVE-2026-34944: CWE-248: Uncaught Exception in bytecodealliance wasmtime
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Wasmtime, a WebAssembly runtime by bytecodealliance, has a vulnerability (CVE-2026-34944) related to its compilation of the f64x2.splat instruction on x86-64 systems with SSE3 disabled. The Cranelift compiler may load 8 extra bytes beyond what is necessary. If signals-based traps are disabled, this leads to an uncaught segmentation fault due to loading from unmapped guard pages. If guard pages are disabled, out-of-sandbox data could be loaded, but this data remains inaccessible to WebAssembly guests. This vulnerability is fixed in wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
Potential Impact
The vulnerability can cause an uncaught segmentation fault, potentially leading to runtime crashes. In configurations where guard pages are disabled, it may allow loading of out-of-sandbox data, though this data is not visible to WebAssembly guests, limiting the impact. There are no known reports of exploitation in the wild. The CVSS 4.1 score reflects a medium severity with local attack vector and partial user interaction required.
Mitigation Recommendations
A fix is available in wasmtime versions 24.0.7, 36.0.7, 42.0.2, and 43.0.1. Users should upgrade to one of these versions to remediate the vulnerability. Since the vendor advisory indicates these versions contain the fix, applying the official update is the recommended mitigation. No additional mitigations are specified or required.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-03-31T17:27:08.660Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d7f88c1cc7ad14da0c16f7
Added to database: 4/9/2026, 7:05:48 PM
Last enriched: 4/17/2026, 12:01:15 PM
Last updated: 5/25/2026, 12:23:26 PM
Views: 83
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