MediumFix available
golang-1.19, golang-1.24 and 1 more products — security advisory
(*x509.Certificate).VerifyHostname previously called matchHostnames in a loop over all DNS Subject Alternative Name (SAN) entries. This caused strings.Split(host, ".") to execute repeatedly on the same input hostname. With a large DNS SAN list, verification costs scaled quadratically based on the number of SAN entries multiplied by the hostname's label count. Because x509.Verify validates hostnames before building the certificate chain, this overhead occurred even for untrusted certificates.
- Products
- golang-1.19, golang-1.24, golang-1.26
- Affected versions
- 1.19.10-1, 1.19.10-2, 1.19.11-1, 1.19.12-1, 1.19.12-2, 1.19.12-2~bpo11+1, 1.19.12-2~bpo12+1, 1.19.13-1, 1.19.13-1~bpo11+1, 1.19.13-1~bpo12+1, 1.19.8-2, 1.19.9-1, 1.24.12-1, 1.24.13-1, 1.24.13-2, 1.24.4-1, 1.24.4-2, 1.24.4-3, 1.24.4-4, 1.24.7-1, 1.24.8-1, 1.24.9-1, 1.26.0-1, 1.26.1-1, 1.26.2-1, 1.26.2-2, 1.26.2-3, 1.26.3-1, 1.26.3-1~bpo13+1, 1.26.3-2, 1.26.3-2~bpo13+1, 1.26.4-1~bpo13+1, 1.26~rc2-1, 1.26~rc3-1, 1.26~rc3-2
- Fixed versions
- 1.26.4-1
- CVEs
- CVE-2026-27145
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 30 Oct 2026, 06:34 UTC · Revision 1
Source evidence
(*x509.Certificate).VerifyHostname previously called matchHostnames in a loop over all DNS Subject Alternative Name (SAN) entries. This caused strings.Split(host, ".") to execute repeatedly on the same input hostname. With a large DNS SAN list, verification costs scaled quadratically based on the number of SAN entries multiplied by the hostname's label count. Because x509.Verify validates hostnames before building the certificate chain, this overhead occurred even for untrusted certificates.
osv:DEBIAN-CVE-2026-27145
golang-1.19
Fixed versions: Not specified
golang-1.24
Fixed versions: Not specified
golang-1.26
Fixed versions: 1.26.4-1
Complete source record
{
"id": "024be12946735b6c2136d29802a0e0455d03bdbf73ead3ff21da216f903aff1a",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-27145",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-27145",
"summary": "(*x509.Certificate).VerifyHostname previously called matchHostnames in a loop over all DNS Subject Alternative Name (SAN) entries. This caused strings.Split(host, \".\") to execute repeatedly on the same input hostname. With a large DNS SAN list, verification costs scaled quadratically based on the number of SAN entries multiplied by the hostname's label count. Because x509.Verify validates hostnames before building the certificate chain, this overhead occurred even for untrusted certificates.",
"evidence": "osv:DEBIAN-CVE-2026-27145",
"products": [
{
"name": {
"value": "golang-1.19",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.19.10-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.10-2",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.11-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.12-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.12-2",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.12-2~bpo11+1",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.12-2~bpo12+1",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.13-1",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.13-1~bpo11+1",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.13-1~bpo12+1",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.8-2",
"evidence": "/affected/0/versions"
},
{
"value": "1.19.9-1",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "golang-1.24",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "1.24.12-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.13-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.13-2",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.4-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.4-2",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.4-3",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.4-4",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.7-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.8-1",
"evidence": "/affected/1/versions"
},
{
"value": "1.24.9-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "golang-1.26",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "1.26.4-1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "1.26.0-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.26.1-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.26.2-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.26.2-2",
"evidence": "/affected/2/versions"
},
{
"value": "1.26.2-3",
"evidence": "/affected/2/versions"
},
{
"value": "1.26.3-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.26.3-1~bpo13+1",
"evidence": "/affected/2/versions"
},
{
"value": "1.26.3-2",
"evidence": "/affected/2/versions"
},
{
"value": "1.26.3-2~bpo13+1",
"evidence": "/affected/2/versions"
},
{
"value": "1.26.4-1~bpo13+1",
"evidence": "/affected/2/versions"
},
{
"value": "1.26~rc2-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.26~rc3-1",
"evidence": "/affected/2/versions"
},
{
"value": "1.26~rc3-2",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "medium",
"structured": {
"id": "DEBIAN-CVE-2026-27145",
"aliases": [
"DEBIAN-CVE-2026-27145"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "golang-1.19",
"purl": "pkg:deb/debian/golang-1.19?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"1.19.10-1",
"1.19.10-2",
"1.19.11-1",
"1.19.12-1",
"1.19.12-2",
"1.19.12-2~bpo11+1",
"1.19.12-2~bpo12+1",
"1.19.13-1",
"1.19.13-1~bpo11+1",
"1.19.13-1~bpo12+1",
"1.19.8-2",
"1.19.9-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27145.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "golang-1.24",
"purl": "pkg:deb/debian/golang-1.24?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"1.24.12-1",
"1.24.13-1",
"1.24.13-2",
"1.24.4-1",
"1.24.4-2",
"1.24.4-3",
"1.24.4-4",
"1.24.7-1",
"1.24.8-1",
"1.24.9-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27145.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.26.4-1"
}
]
}
],
"package": {
"name": "golang-1.26",
"purl": "pkg:deb/debian/golang-1.26?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"1.26.0-1",
"1.26.1-1",
"1.26.2-1",
"1.26.2-2",
"1.26.2-3",
"1.26.3-1",
"1.26.3-1~bpo13+1",
"1.26.3-2",
"1.26.3-2~bpo13+1",
"1.26.4-1~bpo13+1",
"1.26~rc2-1",
"1.26~rc3-1",
"1.26~rc3-2"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-27145.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-12T11:00:43.134055512Z",
"provider": "osv",
"upstream": [
"CVE-2026-27145"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-27145"
]
},
"related_cves": [
{
"value": "CVE-2026-27145",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 299771,
"published_at": "2026-06-02T23:16:35.57+00:00"
}