Gardener: Authorization Bypass via Group Subject Injection
## Overview The `manage-members` custom verb authorization check in the Gardener API server's `customverbauthorizer` admission plugin can be bypassed by adding `Group` or `ServiceAccount` subjects to a Project's member list. The check is documented as controlling "human users or groups", but the implementation only gates changes to `User`-kind subjects. A project admin (without `manage-members` permission) can add arbitrary Group subjects - including `system:authenticated` - granting all authenticated users full project-level access. ## Technical Details The official Gardener documentation at `docs/usage/project/projects.md:90-92` explicitly states: However, the `mustCheckProjectMembers()` function at `admission.go` compares old and new member lists using `findHumanUsersWithRoles()`, which only tracks subjects where `isHumanUser()` returns true: ```go func mustCheckProjectMembers(oldMembers, members []core.ProjectMember, owner *rbacv1.Subject, userInfo user.Info) bool { if apiequality.Semantic.DeepEqual(oldMembers, members) { return false } if userIsOwner(userInfo, owner) { return false } var oldHumanUsers, newHumanUsers = findHumanUsersWithRoles(oldMembers), findHumanUsersWithRoles(members) // ... return !oldHumanUsers.Equal(newHumanUsers) } ``` The `isHumanUser()` function at `admission.go` only matches `Kind == "User"`: ```go func isHumanUser(subject rbacv1.Subject) bool { return subject.Kind == rbacv1.UserKind && !strings.HasPrefix(subject.Name, serviceaccount.ServiceAcco
GHSA-gfjv-gqf2-c888
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:GHSA-gfjv-gqf2-c888
github.com/gardener/gardener
Source reference: /affected/0/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.142.6
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
gardener/gardener
Source reference: /affected/1/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.143.3
Source reference:
/affected/1/ranges - Prerequisites
- Not stated in this record
gardener/gardener
Source reference: /affected/2/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.144.2
Source reference:
/affected/2/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "SEMVER",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.142.6"
}
]
}
],
"package": {
"name": "github.com/gardener/gardener",
"purl": "pkg:golang/github.com/gardener/gardener",
"ecosystem": "Go"
},
"database_specific": {
"source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-gfjv-gqf2-c888/GHSA-gfjv-gqf2-c888.json"
}
},
{
"ranges": [
{
"type": "SEMVER",
"events": [
{
"introduced": "1.143.0"
},
{
"fixed": "1.143.3"
}
]
}
],
"package": {
"name": "gardener/gardener",
"purl": "pkg:golang/gardener/gardener",
"ecosystem": "Go"
},
"database_specific": {
"source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-gfjv-gqf2-c888/GHSA-gfjv-gqf2-c888.json"
}
},
{
"ranges": [
{
"type": "SEMVER",
"events": [
{
"introduced": "1.144.0"
},
{
"fixed": "1.144.2"
}
]
}
],
"package": {
"name": "gardener/gardener",
"purl": "pkg:golang/gardener/gardener",
"ecosystem": "Go"
},
"database_specific": {
"source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-gfjv-gqf2-c888/GHSA-gfjv-gqf2-c888.json"
}
}
]- Related CVEs
- CVE-2026-79767
Source reference:
/aliases
Publisher severity
No explicit severity was provided.
- Event
- #63875 · Revision 1
- Added to Heist Feed
- Publisher date