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CVE-2026-79767 medium CVSS 5.5

Authorization Flaw in github.com/gardener/gardener (CVE-2026-79767)

Summary

Vulnerability in github.com/gardener/gardener (CVE-2026-79767). Data can be tampered with by attackers. Exploitable via customverbauthorizer. Mitigation: upgrade to 1.142.6 or later.

Original description

The description as published by the source.

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:

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":

func isHumanUser(subject rbacv1.Subject) bool {
    return subject.Kind == rbacv1.UserKind && !strings.H…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-79767 has been found in github.com/gardener/gardener.
Attackers can target a specific entry point like customverbauthorizer over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 5.5/10.
What to do: upgrade github.com/gardener/gardener to 1.142.6 or later.
If unsure, ask your IT team or search "github.com/gardener/gardener CVE-2026-79767" on the vendor's site.

CVE-2026-79767 (github.com/gardener/gardener) — CWE-863 / CVSS v3 5.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: customverbauthorizer / Group / ServiceAccount / User
Patched: 1.142.6 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Incorrect authorization (CWE-863) exists in github.com/gardener/gardener. Attackers reach the vulnerable code path via customverbauthorizer.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/gardener/gardener. Attack surface: customverbauthorizer / Group / ServiceAccount / User.

🔥 Severity

Severity: Medium (CVSS 5.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 1.142.6.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/gardener/gardener' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'github.com/gardener/gardener' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で github.com/gardener/gardener を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade github.com/gardener/gardener to 1.142.6

    ステージング環境で 1.142.6 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

go github.com/gardener/gardener
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.142.6"}]}]
go gardener/gardener
[{"type":"SEMVER","events":[{"introduced":"1.144.0"},{"fixed":"1.144.2"}]}]

References

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