rust-wasmtime — security advisory
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings into the Component Model's utf16 or latin1+utf16 encodings improperly verified the alignment of reallocated strings. This meant that unaligned pointers could be passed to the host for transcoding which would trigger a host panic. This panic is possible to trigger from malicious guests which transfer very specific strings across components with specific addresses. Host panics are considered a DoS vector in Wasmtime as the panic conditions are controlled by the guest in this situation. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
- Products
- rust-wasmtime
- Affected versions
- 10.0.1+dfsg-7, 15.0.1+dfsg-4, 16.0.0+dfsg-2, 16.0.0+dfsg-3, 26.0.1+dfsg-3, 26.0.1+dfsg-4, 28.0.1+dfsg-3, 29.0.1+dfsg-5, 36.0.13+dfsg-1, 36.0.5+dfsg-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-34942
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:01 UTC · Revision 1
Source evidence
Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings into the Component Model's utf16 or latin1+utf16 encodings improperly verified the alignment of reallocated strings. This meant that unaligned pointers could be passed to the host for transcoding which would trigger a host panic. This panic is possible to trigger from malicious guests which transfer very specific strings across components with specific addresses. Host panics are considered a DoS vector in Wasmtime as the panic conditions are controlled by the guest in this situation. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
osv:UBUNTU-CVE-2026-34942
rust-wasmtime
Fixed versions: Not specified
rust-wasmtime
Fixed versions: Not specified
rust-wasmtime
Fixed versions: Not specified
rust-wasmtime
Fixed versions: Not specified
Complete source record
{
"id": "c8593d7e111746eeeb4a810ce727e36bfff540c7e4c41f497fb3dda71dbf434f",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-34942",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-34942",
"summary": "Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of transcoding strings into the Component Model's utf16 or latin1+utf16 encodings improperly verified the alignment of reallocated strings. This meant that unaligned pointers could be passed to the host for transcoding which would trigger a host panic. This panic is possible to trigger from malicious guests which transfer very specific strings across components with specific addresses. Host panics are considered a DoS vector in Wasmtime as the panic conditions are controlled by the guest in this situation. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.",
"evidence": "osv:UBUNTU-CVE-2026-34942",
"products": [
{
"name": {
"value": "rust-wasmtime",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "10.0.1+dfsg-7",
"evidence": "/affected/0/versions"
},
{
"value": "15.0.1+dfsg-4",
"evidence": "/affected/0/versions"
},
{
"value": "16.0.0+dfsg-2",
"evidence": "/affected/0/versions"
},
{
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"evidence": "/affected/0/versions"
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{
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"affected_versions": [
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{
"name": {
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"evidence": "/affected/2/package/name"
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"prerequisites": [],
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"affected_versions": [
{
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"evidence": "/affected/2/versions"
},
{
"value": "36.0.13+dfsg-1",
"evidence": "/affected/2/versions"
}
]
},
{
"name": {
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"evidence": "/affected/3/package/name"
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"prerequisites": [],
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"affected_versions": [
{
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"evidence": "/affected/3/versions"
},
{
"value": "26.0.1+dfsg-4",
"evidence": "/affected/3/versions"
},
{
"value": "28.0.1+dfsg-3",
"evidence": "/affected/3/versions"
},
{
"value": "29.0.1+dfsg-5",
"evidence": "/affected/3/versions"
},
{
"value": "36.0.5+dfsg-1",
"evidence": "/affected/3/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "UBUNTU-CVE-2026-34942",
"aliases": [
"UBUNTU-CVE-2026-34942"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L"
},
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
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"introduced": "0"
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}
],
"package": {
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"purl": "pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=noble",
"ecosystem": "Ubuntu:24.04:LTS"
},
"versions": [
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"15.0.1+dfsg-4",
"16.0.0+dfsg-2",
"16.0.0+dfsg-3"
],
"database_specific": {
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},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "librust-cranelift-dev",
"binary_version": "0.103.0+16.0.0+dfsg-3"
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]
}
},
{
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"package": {
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"purl": "pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=questing",
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},
"versions": [
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{
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"purl": "pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=stonking",
"ecosystem": "Ubuntu:26.10"
},
"versions": [
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"36.0.13+dfsg-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34942.json"
},
"ecosystem_specific": {
"binaries": [
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}
]
}
},
{
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"package": {
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"purl": "pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=resolute",
"ecosystem": "Ubuntu:26.04:LTS"
},
"versions": [
"26.0.1+dfsg-3",
"26.0.1+dfsg-4",
"28.0.1+dfsg-3",
"29.0.1+dfsg-5",
"36.0.5+dfsg-1"
],
"database_specific": {
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},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "librust-cranelift-dev",
"binary_version": "0.123.5+36.0.5+dfsg-1"
}
]
}
}
],
"modified": "2026-10-17T13:00:02.430041948Z",
"provider": "osv",
"upstream": [
"CVE-2026-34942"
],
"references": [
"https://ubuntu.com/security/CVE-2026-34942",
"https://www.cve.org/CVERecord?id=CVE-2026-34942",
"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-jxhv-7h78-9775"
]
},
"related_cves": [
{
"value": "CVE-2026-34942",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/1/score"
},
"source_id": "core-osv",
"document_id": 360169,
"published_at": "2026-04-09T19:16:00+00:00"
}