kbd — security advisory
`openvt -u` is intended to identify the owner of the current VT and then execute `login` as that user from a privileged context. In the documented `kbrequest`/init usage, the ownership test in `authenticate_user()` relies on `stat("/proc//fd/0")`. `stat()` on `/proc//fd/0` follows the symlink to the underlying TTY device node. As a result, `buf.st_uid` reflects the owner of the TTY node rather than the owner of the process holding the file descriptor. If the TTY owner returns to `root` or the getty owner after logout while an unprivileged process still has `fd 0` attached to that TTY, the check can incorrectly treat that process as belonging to the privileged console owner. Once that check succeeds, the `-u` path executes a passwordless login as the selected user. In the documented `kbrequest`/init deployment using `openvt -us`, this can result in passwordless `login -f root` on the spawned VT. This report establishes that privilege escalation path for that documented deployment; it does not claim equivalent reachability for deployments that do not use `openvt -u` from a privileged `kbrequest`/init path.
- Products
- kbd
- Affected versions
- 2.10.0-1, 2.5.1-1, 2.6.4-1, 2.6.4-2, 2.6.4-3, 2.7.1-1, 2.7.1-2, 2.7.1-2+exp1, 2.7~rc1-1, 2.9.0-1
- Fixed versions
- 2.10.0-1
- CVEs
- CVE-2026-72693
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 30 Oct 2026, 06:03 UTC · Revision 1
Source evidence
`openvt -u` is intended to identify the owner of the current VT and then execute `login` as that user from a privileged context. In the documented `kbrequest`/init usage, the ownership test in `authenticate_user()` relies on `stat("/proc//fd/0")`. `stat()` on `/proc//fd/0` follows the symlink to the underlying TTY device node. As a result, `buf.st_uid` reflects the owner of the TTY node rather than the owner of the process holding the file descriptor. If the TTY owner returns to `root` or the getty owner after logout while an unprivileged process still has `fd 0` attached to that TTY, the check can incorrectly treat that process as belonging to the privileged console owner. Once that check succeeds, the `-u` path executes a passwordless login as the selected user. In the documented `kbrequest`/init deployment using `openvt -us`, this can result in passwordless `login -f root` on the spawned VT. This report establishes that privilege escalation path for that documented deployment; it does not claim equivalent reachability for deployments that do not use `openvt -u` from a privileged `kbrequest`/init path.
osv:DEBIAN-CVE-2026-72693
kbd
Fixed versions: Not specified
kbd
Fixed versions: Not specified
kbd
Fixed versions: 2.10.0-1
Complete source record
{
"id": "60aca573d3b023536e8c6903ee900253cfc515029360ac163dde2cf5b344a999",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-72693",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-72693",
"summary": "`openvt -u` is intended to identify the owner of the current VT and then execute `login` as that user from a privileged context. In the documented `kbrequest`/init usage, the ownership test in `authenticate_user()` relies on `stat(\"/proc//fd/0\")`. `stat()` on `/proc//fd/0` follows the symlink to the underlying TTY device node. As a result, `buf.st_uid` reflects the owner of the TTY node rather than the owner of the process holding the file descriptor. If the TTY owner returns to `root` or the getty owner after logout while an unprivileged process still has `fd 0` attached to that TTY, the check can incorrectly treat that process as belonging to the privileged console owner. Once that check succeeds, the `-u` path executes a passwordless login as the selected user. In the documented `kbrequest`/init deployment using `openvt -us`, this can result in passwordless `login -f root` on the spawned VT. This report establishes that privilege escalation path for that documented deployment; it does not claim equivalent reachability for deployments that do not use `openvt -u` from a privileged `kbrequest`/init path.",
"evidence": "osv:DEBIAN-CVE-2026-72693",
"products": [
{
"name": {
"value": "kbd",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.10.0-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.5.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.6.4-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.6.4-2",
"evidence": "/affected/0/versions"
},
{
"value": "2.6.4-3",
"evidence": "/affected/0/versions"
},
{
"value": "2.7.1-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.7.1-2",
"evidence": "/affected/0/versions"
},
{
"value": "2.7.1-2+exp1",
"evidence": "/affected/0/versions"
},
{
"value": "2.7~rc1-1",
"evidence": "/affected/0/versions"
},
{
"value": "2.9.0-1",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "kbd",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "2.10.0-1",
"evidence": "/affected/1/versions"
},
{
"value": "2.7.1-2",
"evidence": "/affected/1/versions"
},
{
"value": "2.7.1-2+exp1",
"evidence": "/affected/1/versions"
},
{
"value": "2.9.0-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "kbd",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "2.10.0-1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "2.7.1-2",
"evidence": "/affected/2/versions"
},
{
"value": "2.7.1-2+exp1",
"evidence": "/affected/2/versions"
},
{
"value": "2.9.0-1",
"evidence": "/affected/2/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "DEBIAN-CVE-2026-72693",
"aliases": [
"DEBIAN-CVE-2026-72693"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "kbd",
"purl": "pkg:deb/debian/kbd?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
"2.10.0-1",
"2.5.1-1",
"2.6.4-1",
"2.6.4-2",
"2.6.4-3",
"2.7.1-1",
"2.7.1-2",
"2.7.1-2+exp1",
"2.7~rc1-1",
"2.9.0-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-72693.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "kbd",
"purl": "pkg:deb/debian/kbd?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"2.10.0-1",
"2.7.1-2",
"2.7.1-2+exp1",
"2.9.0-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-72693.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "2.10.0-1"
}
]
}
],
"package": {
"name": "kbd",
"purl": "pkg:deb/debian/kbd?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"2.7.1-2",
"2.7.1-2+exp1",
"2.9.0-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-72693.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
],
"modified": "2026-10-12T05:00:12.109036546Z",
"provider": "osv",
"upstream": [
"CVE-2026-72693"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-72693"
]
},
"related_cves": [
{
"value": "CVE-2026-72693",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 298618,
"published_at": "2026-08-11T09:17:14.34+00:00"
}