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 contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This panic only affects wasmtime's implementation of lifting into Val, not when using the flags! macro. This additionally only affects flags-typed values which are part of a WIT interface. This has the risk of being a guest-controlled panic within the host which Wasmtime considers a DoS vector. 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-2026-34943
- 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 contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This panic only affects wasmtime's implementation of lifting into Val, not when using the flags! macro. This additionally only affects flags-typed values which are part of a WIT interface. This has the risk of being a guest-controlled panic within the host which Wasmtime considers a DoS vector. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.
osv:UBUNTU-CVE-2026-34943
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": "82558e8e9189b028650db1df52bf20856b0ed3f59f13786d84af40b3bf66dd64",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-34943",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-34943",
"summary": "Wasmtime is a runtime for WebAssembly. Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This panic only affects wasmtime's implementation of lifting into Val, not when using the flags! macro. This additionally only affects flags-typed values which are part of a WIT interface. This has the risk of being a guest-controlled panic within the host which Wasmtime considers a DoS vector. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1.",
"evidence": "osv:UBUNTU-CVE-2026-34943",
"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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{
"name": {
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"evidence": "/affected/1/package/name"
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"affected_versions": [
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"evidence": "/affected/1/versions"
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]
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{
"name": {
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"evidence": "/affected/2/package/name"
},
"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": "high",
"structured": {
"id": "UBUNTU-CVE-2026-34943",
"aliases": [
"UBUNTU-CVE-2026-34943"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
},
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"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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},
"versions": [
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},
"ecosystem_specific": {
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},
{
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"package": {
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"purl": "pkg:deb/ubuntu/rust-wasmtime?arch=source&distro=stonking",
"ecosystem": "Ubuntu:26.10"
},
"versions": [
"36.0.5+dfsg-1",
"36.0.13+dfsg-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34943.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "librust-cranelift-dev",
"binary_version": "0.123.13+36.0.13+dfsg-1"
}
]
}
},
{
"ranges": [
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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": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-34943.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "librust-cranelift-dev",
"binary_version": "0.123.5+36.0.5+dfsg-1"
}
]
}
}
],
"modified": "2026-10-17T13:00:02.508902683Z",
"provider": "osv",
"upstream": [
"CVE-2026-34943"
],
"references": [
"https://ubuntu.com/security/CVE-2026-34943",
"https://www.cve.org/CVERecord?id=CVE-2026-34943",
"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-m758-wjhj-p3jq"
]
},
"related_cves": [
{
"value": "CVE-2026-34943",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/1/score"
},
"source_id": "core-osv",
"document_id": 360171,
"published_at": "2026-04-09T19:16:00+00:00"
}