osbuild-composer: Fix of CVE-2026-39821
- CVE-2026-39821: reject xn-- Punycode labels that decode to an all-ASCII label in the vendored golang.org/x/net/idna, so ToASCII and ToUnicode no longer resolve names such as xn--example-.com to example.com without an error, preventing privilege escalation in programs that perform privilege checks on the ASCII hostname - CVE-2026-39821: rebuild against golang >= 1.22.9-1.el9_2.tuxcare.els19 so the copy of golang.org/x/net/idna vendored into the Go standard library, which net/http uses to convert outbound request hosts, carries the same rejection
- Products
- osbuild-composer, osbuild-composer-core, osbuild-composer-dnf-json, osbuild-composer-tests, osbuild-composer-worker
- Affected versions
- Not specified
- Fixed versions
- 76-2.el9_2.2.alma.tuxcare.els10
- CVEs
- CVE-2026-39821
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 10:45 UTC · Revision 1
Source evidence
- CVE-2026-39821: reject xn-- Punycode labels that decode to an all-ASCII label in the vendored golang.org/x/net/idna, so ToASCII and ToUnicode no longer resolve names such as xn--example-.com to example.com without an error, preventing privilege escalation in programs that perform privilege checks on the ASCII hostname - CVE-2026-39821: rebuild against golang >= 1.22.9-1.el9_2.tuxcare.els19 so the copy of golang.org/x/net/idna vendored into the Go standard library, which net/http uses to convert outbound request hosts, carries the same rejection
osv:CLSA-2026-1789640442
osbuild-composer
Fixed versions: 76-2.el9_2.2.alma.tuxcare.els10
osbuild-composer-core
Fixed versions: 76-2.el9_2.2.alma.tuxcare.els10
osbuild-composer-dnf-json
Fixed versions: 76-2.el9_2.2.alma.tuxcare.els10
osbuild-composer-tests
Fixed versions: 76-2.el9_2.2.alma.tuxcare.els10
osbuild-composer-worker
Fixed versions: 76-2.el9_2.2.alma.tuxcare.els10
Complete source record
{
"id": "b666601d05a4c68b291dc4cab7bb4e48fe7d4843014589e4db26d30cb23093a8",
"url": "https://osv.dev/vulnerability/CLSA-2026-1789640442",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "osbuild-composer: Fix of CVE-2026-39821",
"summary": "- CVE-2026-39821: reject xn-- Punycode labels that decode to an all-ASCII label in the vendored golang.org/x/net/idna, so ToASCII and ToUnicode no longer resolve names such as xn--example-.com to example.com without an error, preventing privilege escalation in programs that perform privilege checks on the ASCII hostname - CVE-2026-39821: rebuild against golang >= 1.22.9-1.el9_2.tuxcare.els19 so the copy of golang.org/x/net/idna vendored into the Go standard library, which net/http uses to convert outbound request hosts, carries the same rejection",
"evidence": "osv:CLSA-2026-1789640442",
"products": [
{
"name": {
"value": "osbuild-composer",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "76-2.el9_2.2.alma.tuxcare.els10",
"evidence": "/affected/0/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "osbuild-composer-core",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "76-2.el9_2.2.alma.tuxcare.els10",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "osbuild-composer-dnf-json",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "76-2.el9_2.2.alma.tuxcare.els10",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "osbuild-composer-tests",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "76-2.el9_2.2.alma.tuxcare.els10",
"evidence": "/affected/3/ranges"
}
],
"affected_versions": []
},
{
"name": {
"value": "osbuild-composer-worker",
"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "76-2.el9_2.2.alma.tuxcare.els10",
"evidence": "/affected/4/ranges"
}
],
"affected_versions": []
}
],
"severity": "unknown",
"structured": {
"id": "CLSA-2026-1789640442",
"aliases": [
"CLSA-2026-1789640442"
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "76-2.el9_2.2.alma.tuxcare.els10"
}
]
}
],
"package": {
"name": "osbuild-composer",
"purl": "pkg:rpm/tuxcare/osbuild-composer?distro=almalinux-9.2",
"ecosystem": "TuxCare:AlmaLinux:9.2"
},
"database_specific": {
"source": "https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/almalinux9.2esu/CLSA-2026-1789640442.json"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "76-2.el9_2.2.alma.tuxcare.els10"
}
]
}
],
"package": {
"name": "osbuild-composer-core",
"purl": "pkg:rpm/tuxcare/osbuild-composer-core?distro=almalinux-9.2",
"ecosystem": "TuxCare:AlmaLinux:9.2"
},
"database_specific": {
"source": "https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/almalinux9.2esu/CLSA-2026-1789640442.json"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "76-2.el9_2.2.alma.tuxcare.els10"
}
]
}
],
"package": {
"name": "osbuild-composer-dnf-json",
"purl": "pkg:rpm/tuxcare/osbuild-composer-dnf-json?distro=almalinux-9.2",
"ecosystem": "TuxCare:AlmaLinux:9.2"
},
"database_specific": {
"source": "https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/almalinux9.2esu/CLSA-2026-1789640442.json"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "76-2.el9_2.2.alma.tuxcare.els10"
}
]
}
],
"package": {
"name": "osbuild-composer-tests",
"purl": "pkg:rpm/tuxcare/osbuild-composer-tests?distro=almalinux-9.2",
"ecosystem": "TuxCare:AlmaLinux:9.2"
},
"database_specific": {
"source": "https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/almalinux9.2esu/CLSA-2026-1789640442.json"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "76-2.el9_2.2.alma.tuxcare.els10"
}
]
}
],
"package": {
"name": "osbuild-composer-worker",
"purl": "pkg:rpm/tuxcare/osbuild-composer-worker?distro=almalinux-9.2",
"ecosystem": "TuxCare:AlmaLinux:9.2"
},
"database_specific": {
"source": "https://github.com/cloudlinux/tuxcare-osv/tree/main/data/els_os/almalinux9.2esu/CLSA-2026-1789640442.json"
}
}
],
"modified": "2026-10-26T09:30:49.009167707Z",
"provider": "osv",
"upstream": [
"CVE-2026-39821"
],
"references": [
"https://errata.tuxcare.com/els_os/almalinux9.2esu/CLSA-2026-1789640442.html",
"https://nvd.nist.gov/vuln/detail/CVE-2026-39821"
]
},
"related_cves": [
{
"value": "CVE-2026-39821",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": null
},
"source_id": "core-osv",
"document_id": 447259,
"published_at": "2026-09-17T10:20:53+00:00"
}