Medium
cosign — security advisory
Cosign provides code signing and transparency for containers and binaries. Prior to 3.0.6 and 2.6.3, cosign verify-blob-attestation may erroneously report a "Verified OK" result for attestations with malformed payloads or mismatched predicate types. For old-format bundles and detached signatures, this was due to a logic flaw in the error handling of the predicate type validation. For new-format bundles, the predicate type validation was bypassed completely. This vulnerability is fixed in 3.0.6 and 2.6.3.
- Products
- cosign
- Affected versions
- 2.4.3-1, 2.5.0-2, 2.5.0-2build1, 2.6.2-1, 2.6.2-1ubuntu0.26.04.1~esm1, 3.1.1-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-39395
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:43 UTC · Revision 1
Source evidence
Cosign provides code signing and transparency for containers and binaries. Prior to 3.0.6 and 2.6.3, cosign verify-blob-attestation may erroneously report a "Verified OK" result for attestations with malformed payloads or mismatched predicate types. For old-format bundles and detached signatures, this was due to a logic flaw in the error handling of the predicate type validation. For new-format bundles, the predicate type validation was bypassed completely. This vulnerability is fixed in 3.0.6 and 2.6.3.
osv:UBUNTU-CVE-2026-39395
cosign
Fixed versions: Not specified
cosign
Fixed versions: Not specified
cosign
Fixed versions: Not specified
Complete source record
{
"id": "ca8ede9af67a00d393b1ab68fb7fa347dd55fb160bbb4aee60b7a2e8db64189e",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-39395",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2026-39395",
"summary": "Cosign provides code signing and transparency for containers and binaries. Prior to 3.0.6 and 2.6.3, cosign verify-blob-attestation may erroneously report a \"Verified OK\" result for attestations with malformed payloads or mismatched predicate types. For old-format bundles and detached signatures, this was due to a logic flaw in the error handling of the predicate type validation. For new-format bundles, the predicate type validation was bypassed completely. This vulnerability is fixed in 3.0.6 and 2.6.3.",
"evidence": "osv:UBUNTU-CVE-2026-39395",
"products": [
{
"name": {
"value": "cosign",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.4.3-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.5.0-2",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "cosign",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.6.2-1",
"evidence": "/affected/1/versions"
},
{
"value": "3.1.1-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "cosign",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.5.0-2",
"evidence": "/affected/2/versions"
},
{
"value": "2.5.0-2build1",
"evidence": "/affected/2/versions"
},
{
"value": "2.6.2-1",
"evidence": "/affected/2/versions"
},
{
"value": "2.6.2-1ubuntu0.26.04.1~esm1",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "UBUNTU-CVE-2026-39395",
"aliases": [
"UBUNTU-CVE-2026-39395"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N"
},
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "cosign",
"purl": "pkg:deb/ubuntu/cosign?arch=source&distro=questing",
"ecosystem": "Ubuntu:25.10"
},
"versions": [
"2.4.3-1",
"2.5.0-2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-39395.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "cosign",
"binary_version": "2.5.0-2"
},
{
"binary_name": "golang-github-sigstore-cosign-dev",
"binary_version": "2.5.0-2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "cosign",
"purl": "pkg:deb/ubuntu/cosign?arch=source&distro=stonking",
"ecosystem": "Ubuntu:26.10"
},
"versions": [
"2.6.2-1",
"3.1.1-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-39395.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "cosign",
"binary_version": "3.1.1-1"
},
{
"binary_name": "golang-github-sigstore-cosign-dev",
"binary_version": "3.1.1-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "cosign",
"purl": "pkg:deb/ubuntu/cosign?arch=source&distro=esm-apps%2Fresolute",
"ecosystem": "Ubuntu:Pro:26.04:LTS"
},
"versions": [
"2.5.0-2",
"2.5.0-2build1",
"2.6.2-1",
"2.6.2-1ubuntu0.26.04.1~esm1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-39395.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "cosign",
"binary_version": "2.6.2-1ubuntu0.26.04.1~esm1"
},
{
"binary_name": "golang-github-sigstore-cosign-dev",
"binary_version": "2.6.2-1ubuntu0.26.04.1~esm1"
}
]
}
}
],
"modified": "2026-10-17T12:58:52.538175133Z",
"provider": "osv",
"upstream": [
"CVE-2026-39395"
],
"references": [
"https://ubuntu.com/security/CVE-2026-39395",
"https://www.cve.org/CVERecord?id=CVE-2026-39395",
"https://github.com/sigstore/cosign/security/advisories/GHSA-w6c6-c85g-mmv6"
]
},
"related_cves": [
{
"value": "CVE-2026-39395",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/1/score"
},
"source_id": "core-osv",
"document_id": 359125,
"published_at": "2026-04-07T20:16:00+00:00"
}