Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-34944
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 3 Nov 2026, 16:45 UTC · Revision 1
Source evidence
Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64
core-osv · Original sourcePublished 9 Apr 2026, 18:38 UTC
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.
osv:CVE-2026-34944
Complete source record
{
"id": "e8d9c8bb7e09cc60ff5cdeca9d8d747c7ac8813801c8c93f5c40293feed52892",
"url": "https://osv.dev/vulnerability/CVE-2026-34944",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Wasmtime segfault or unused out-of-sandbox load with `f64x2.splat` operator on x86-64",
"summary": "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.",
"evidence": "osv:CVE-2026-34944",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-34944",
"aliases": [
"CVE-2026-34944",
"GHSA-qqfj-4vcm-26hv",
"RUSTSEC-2026-0087"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/bytecodealliance/wasmtime",
"type": "GIT",
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"introduced": "0"
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{
"fixed": "a15daff0bfc965d1656ddcf9beaa1d085c3a7410"
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"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-34944.json"
}
}
],
"modified": "2026-10-28T02:30:30.753486785Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34944.json",
"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-qqfj-4vcm-26hv",
"https://nvd.nist.gov/vuln/detail/CVE-2026-34944"
],
"provider_metadata": {
"cwe_ids": [
"CWE-248"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34944.json"
}
},
"related_cves": [
{
"value": "CVE-2026-34944",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 497530,
"published_at": "2026-04-09T18:38:16.182+00:00"
}