CVE-2025-1767: Kubernetes GitRepo Volume Vulnerability

Executive Summary

CVE-2025-1767 is a medium-severity vulnerability affecting Kubernetes clusters that utilize the deprecated in-tree gitRepo volume feature. This vulnerability allows an attacker with sufficient privileges to exploit the gitRepo volume to access local Git repositories from other pods on the same node. The vulnerability has a CVSS v3.1 score of 6.5 (Medium) and is classified under CWE-20 (Improper Input Validation). Since the gitRepo volume feature is deprecated and no longer maintained, clusters still relying on this feature remain vulnerable unless mitigated.

This vulnerability highlights the risks of using deprecated features in critical infrastructure and underscores the importance of adhering to security best practices in Kubernetes environments.

Technical Details

Affected Systems and Components

• Affected Component: Kubernetes kubelet with in-tree gitRepo volume support.
• Vulnerable Feature: In-tree gitRepo volume, which allows pods to clone Git repositories during initialization.
• Affected Versions: All versions of Kubernetes that support the gitRepo volume feature.

The gitRepo volume feature is used to clone a Git repository into a pod's volume. However, due to improper isolation and validation, an attacker can exploit this feature to access sensitive .git directories from other pods on the same node.

Vulnerability Metrics

• CVSS v3.1 Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: High
  • User Interaction: None
  • Scope: Unchanged
  • Confidentiality Impact: High
  • Integrity Impact: High
  • Availability Impact: None
• Base Score: 6.5 (Medium)

Root Cause Analysis

The root cause of CVE-2025-1767 lies in the design and implementation of the in-tree gitRepo volume feature. Specifically, the gitRepo volume does not properly isolate or validate the repository paths being cloned, allowing an attacker to target .git directories from other pods on the same node.

Code Analysis

The gitRepo volume is implemented in the Kubernetes kubelet component. When a pod is created with a gitRepo volume, the kubelet clones the specified Git repository into the pod's volume. The vulnerability arises because the gitRepo implementation does not enforce strict validation of the repository path or ensure proper isolation between pods.

Example of Vulnerable Configuration

apiVersion: v1
kind: Pod
metadata:
  name: vulnerable-pod
spec:
  containers:
  - name: app-container
    image: nginx
  volumes:
  - name: git-volume
    gitRepo:
      repository: "/path/to/repository"
      revision: "master"
  volumeMounts:
  - mountPath: "/mnt/repo"
    name: git-volume

In this configuration, the gitRepo volume clones the specified repository into the pod's /mnt/repo directory. However, due to improper validation, an attacker can specify a malicious repository path to access sensitive .git directories from other pods.

Patch Analysis

The Kubernetes maintainers have deprecated the gitRepo volume feature and recommend using alternative methods, such as init containers, to perform Git operations. No direct patch has been provided for this vulnerability since the feature is no longer maintained.

Theoretical Fix

A theoretical fix would involve adding strict validation for the repository field in the gitRepo volume configuration. For example:

diff --git a/pkg/volume/git_repo/git_repo.go b/pkg/volume/git_repo/git_repo.go
index abc123..def456 100644
--- a/pkg/volume/git_repo/git_repo.go
+++ b/pkg/volume/git_repo/git_repo.go
@@ -45,6 +45,10 @@ func (plugin *gitRepoPlugin) NewMounter(spec *volume.Spec, pod *api.Pod, opts vo
        if err != nil {
                return nil, err
        }
+       // Validate repository path
+       if !isValidRepositoryPath(repo.Repository) {
+               return nil, fmt.Errorf("invalid repository path: %s", repo.Repository)
+       }
        return &gitRepoMounter{
                source: repo,
                pod:    pod,
@@ -80,6 +84,12 @@ func cloneGitRepo(repo *api.GitRepoVolumeSource, targetDir string) error {
        return nil
 }

+func isValidRepositoryPath(path string) bool {
+       // Add logic to validate repository path
+       // For example, ensure it does not point to a local directory
+       return !strings.HasPrefix(path, "/")
+}
+
 func (plugin *gitRepoPlugin) NewUnmounter(volumeName string, podUID types.UID) (volume.Unmounter, error) {
        return &gitRepoUnmounter{
                podUID: podUID,

Note: This patch is theoretical and not implemented in the Kubernetes codebase.

Exploitation Techniques

Exploit Scenario

An attacker with create pod permissions can craft a malicious pod configuration to exploit the gitRepo volume and access sensitive .git directories from other pods.

Proof of Concept (PoC)

apiVersion: v1
kind: Pod
metadata:
  name: exploit-pod
spec:
  containers:
  - name: attacker-container
    image: alpine
    command: ["/bin/sh", "-c", "cat /mnt/repo/.git/config"]
  volumes:
  - name: git-volume
    gitRepo:
      repository: "/var/lib/kubelet/pods/target-pod-id/volumes/kubernetes.io~gitRepo/.git"
      revision: "master"
  volumeMounts:
  - mountPath: "/mnt/repo"
    name: git-volume

In this PoC, the attacker specifies a repository path pointing to the .git directory of another pod. When the pod is created, the gitRepo volume clones the targeted .git directory, exposing sensitive information.

Mitigation Strategies

To mitigate CVE-2025-1767, follow these recommendations:

1. Avoid Using Deprecated Features:

   • Replace the gitRepo volume with an init container to perform Git operations. Example:

     apiVersion: v1
     kind: Pod
     metadata:
       name: secure-pod
     spec:
       initContainers:
       - name: git-clone
         image: alpine/git
         command: ["git", "clone", "https://github.com/example/repo.git", "/mnt/repo"]
         volumeMounts:
         - mountPath: "/mnt/repo"
           name: repo-volume
       containers:
       - name: app-container
         image: nginx
         volumeMounts:
         - mountPath: "/mnt/repo"
           name: repo-volume
       volumes:
       - name: repo-volume
         emptyDir: {}
     

2. Enforce Admission Policies:

   • Use a ValidatingAdmissionPolicy or a Restricted pod security standard policy to block the use of gitRepo volumes. Example CEL expression:

     has(object.spec.volumes) || !object.spec.volumes.exists(v, has(v.gitRepo))
     

3. Monitor for Exploitation:

   • Detect pods using the gitRepo volume with the following command:

     kubectl get pods --all-namespaces -o json | jq '.items[] | select(.spec.volumes[].gitRepo.repository | test("^/")) | {name: .metadata.name, namespace: .metadata.namespace, repository: (.spec.volumes[] | select(.gitRepo) | .gitRepo.repository)}'
     

4. Upgrade Kubernetes:

   • Use the latest Kubernetes version and avoid relying on deprecated features.

Timeline of Discovery and Disclosure

References

• Kubernetes GitRepo Volume Deprecation
• Kubernetes Security Advisory
• Red Hat Security Advisory

By understanding and addressing CVE-2025-1767, organizations can secure their Kubernetes clusters and prevent potential exploitation of deprecated features.