Argo CD PostDelete Hook Flaw Bypasses Auth Checks

Argo CD is a declarative GitOps continuous delivery tool for Kubernetes. A critical vulnerability, tracked as CVE-2026-77459, allows attackers to bypass authorization checks when deleting applications. This flaw enables users with write access to an Application's Git repository to create forbidden resources in the target cluster. The issue stems from missing security validations during the PostDelete hook execution phase.

How does the vulnerability work?

The application-controller in Argo CD creates PostDelete resource hooks without applying standard AppProject destination and resource authorization checks. These omitted checks normally include cluster-scoped and namespaced resource allow and deny lists. When an application is deleted, the controller executes these hooks using its own destination-cluster credentials. This behavior differs from how PreSync, Sync, PostSync, and SyncFail hooks are handled, which continue to use normal project security checks.

Who can exploit this flaw?

Any user who can write to an Application's Git repository can exploit this issue. They can commit a delete hook that targets a forbidden namespace, server, group, kind, or resource name. Upon deletion of the Application, the application-controller creates that resource. The reachable impact is bounded by the controller's cluster access but can include cluster-scoped resources and disallowed namespaces. Attackers can also create persistent hook objects and secondary objects created by a hook Job.

Which versions are affected?

The vulnerability affects Argo CD versions from 2.10.0 until 3.3.15, 3.4.10, 3.5.4, and 3.6.0-rc2. Specifically, it impacts versions 2.10.0 through 2.14.21, 3.0.0 through 3.3.14, 3.4.0 through 3.4.9, and 3.5.0 through 3.5.3. The issue is fixed in versions 3.3.15, 3.4.10, 3.5.4, and 3.6.0-rc2. Users running any affected version should update immediately to mitigate the risk of unauthorized resource creation.

What comes next for users?

Users should verify their current Argo CD version against the affected list. If running an affected version, they must upgrade to one of the patched releases. Until updated, teams should restrict write access to Application Git repositories. Monitoring for unexpected resource creation during application deletions can help detect exploitation. The vendor has released fixes for all affected branches, ensuring a path to remediation for all users.

What analysts watch for

Teams usually monitor for unexpected resource creation during application deletion events. Analysts should check whether PostDelete hooks are generating cluster-scoped resources or objects in disallowed namespaces. They must examine the Git history of Application repositories for recent commits adding delete hooks. Reviewing application-controller logs for hook execution without corresponding authorization checks is also vital. Look for persistent hook objects or secondary objects created by hook Jobs that should not exist.

What to do and how to stay safe: Argo CD

• Update Argo CD to version 3.3.15, 3.4.10, 3.5.4, or 3.6.0-rc2 as soon as possible.
• Audit Git repositories for Application definitions to remove any suspicious PostDelete hooks.
• Restrict write access to Application Git repositories to trusted administrators only.
• Monitor Kubernetes clusters for unauthorized resource creation during application deletion events.

Step-by-step guide: Patch Management: Why Updates Fail and How to Fix It

General security guidance from the Sandbox Dispatch newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

What is the CVSS score for CVE-2026-77459?

The CVSS score for CVE-2026-77459 is 9.9, which is rated as Critical.

Which Argo CD versions are patched?

The issue is fixed in versions 3.3.15, 3.4.10, 3.5.4, and 3.6.0-rc2.

Can users with Git access exploit this flaw?

Yes, users who can write to an Application's Git repository can commit a delete hook to create forbidden resources.