Description

Argo Workflows versions 4.1.0 through 4.1.3 contain an authorization bypass vulnerability in ListArchivedWorkflows that fails to apply cluster-scoped access review when the metadata.namespace field selector uses the NotEquals operator. Attackers with namespace-scoped list permissions can use a negated namespace field selector to retrieve archived workflows from all other namespaces, exposing spec arguments, parameter values, and annotations.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.7",
  "pubDate": "2026-09-19T23:17:10.360Z",
  "pubdate": "2026-09-19T23:17:10.360Z",
  "executiveSummary": "Argo Workflows versions 4.1.0 through 4.1.3 are susceptible to an authorization bypass vulnerability within the ListArchivedWorkflows function. This security flaw stems from an improper implementation of access control checks when handling specific field selector queries. An attacker possessing only namespace-scoped list permissions can exploit this logic error to circumvent cluster-scoped access reviews. By utilizing the NotEquals operator in conjunction with the metadata.namespace field selector, a malicious actor can bypass intended namespace boundaries to retrieve archived workflow data from the entire cluster. Successful exploitation leads to unauthorized disclosure of sensitive information, including workflow specifications, input parameter values, and metadata annotations. The impact is significant, as it effectively elevates the access privileges of an otherwise restricted user to encompass cross-namespace visibility, thereby violating the principle of least privilege and exposing potentially confidential execution environments to unauthorized observation.",
  "technicalDetails": "The vulnerability resides in the ListArchivedWorkflows function within the Argo Workflows controller. The root cause is an insecure validation process during the evaluation of field selectors. Specifically, the application fails to correctly enforce cluster-scoped access review permissions when a user submits a query containing the NotEquals (!=) operator targeted at the metadata.namespace field.\nUnder standard conditions, a user with namespace-scoped permissions should be restricted to retrieving archived workflows exclusively within their assigned namespace. However, the logic within ListArchivedWorkflows erroneously treats the negated namespace selector as a broad query filter, failing to trigger the necessary authorization enforcement that would normally verify the user's scope against the cluster-wide archived records.\nThe attack flow proceeds as follows: 1) The attacker authenticates as a user with limited permissions restricted to a single namespace. 2) The attacker issues a request to the ListArchivedWorkflows endpoint, crafting a payload where the field selector is set to metadata.namespace!=<attacker_namespace>. 3) The backend receives the request and parses the field selector. Due to the failure to properly resolve the implications of the NotEquals operator, the application logic assumes the request is valid for all namespaces other than the specified one. 4) The system bypasses the required cluster-level RBAC (Role-Based Access Control) check. 5) The database returns the archived workflows matching the criteria, effectively dumping records from all namespaces the attacker was never intended to access.\nThis vulnerability is present in versions 4.1.0 through 4.1.3 of Argo Workflows. Exploitation is possible by any authenticated user who has the standard 'list' permission for archived workflows within their own namespace. No special privileges beyond this baseline are required. Because the vulnerability lies within the API logic, it is accessible via any interface that communicates with the Argo Workflows API, typically over HTTPS. The payload behavior is strictly read-only, focusing on the unauthorized extraction of sensitive data stored in the workflow specifications and annotations, which may contain secrets or environment-specific configurations."
}