CVE-2025-59538 in argo-cd
Summary
by MITRE • 10/02/2025
Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes. For versions 2.9.0-rc1 through 2.14.19, 3.0.0-rc1 through 3.2.0-rc1, 3.1.6 and 3.0.17, when the webhook.azuredevops.username and webhook.azuredevops.password are not set in the default configuration, the /api/webhook endpoint crashes the entire argocd-server process when it receives an Azure DevOps Push event whose JSON array resource.refUpdates is empty. The slice index [0] is accessed without a length check, causing an index-out-of-range panic. A single unauthenticated HTTP POST is enough to kill the process. This issue is resolved in versions 2.14.20, 3.2.0-rc2, 3.1.8 and 3.0.19.
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Analysis
by VulDB Data Team • 11/25/2025
The vulnerability CVE-2025-59538 affects Argo CD continuous delivery tool versions within specific release ranges including 2.9.0-rc1 through 2.14.19, 3.0.0-rc1 through 3.2.0-rc1, 3.1.6, and 3.0.17. This issue represents a critical denial-of-service condition that stems from improper input validation within the webhook processing mechanism. The vulnerability specifically targets the /api/webhook endpoint which handles Azure DevOps Push events, creating a scenario where a simple malformed HTTP POST request can cause complete system failure.
The technical flaw manifests as an index-out-of-range panic occurring when the Argo CD server processes Azure DevOps webhook events. The system attempts to access the first element of the resource.refUpdates JSON array using slice index [0] without performing a length check first. This primitive programming error directly violates secure coding practices and results in a segmentation fault that terminates the entire argocd-server process. The vulnerability is particularly dangerous because it requires no authentication or authorization to exploit, making it accessible to any external attacker capable of sending HTTP requests to the targeted endpoint.
This vulnerability directly maps to CWE-129, which describes improper validation of array index, and CWE-476, which covers null pointer dereference. The operational impact is severe as a single malicious HTTP POST request can cause complete service disruption requiring manual restart of the argocd-server process. The attack surface is broad since the endpoint is typically exposed to external networks for integration with Azure DevOps services, and the lack of authentication requirements means that any network traffic can potentially trigger this condition. This creates an environment where attackers can easily disrupt continuous delivery pipelines and potentially cause production outages.
The remediation strategy involves upgrading to patched versions including 2.14.20, 3.2.0-rc2, 3.1.8, and 3.0.19 which implement proper array bounds checking. Organizations should also implement network-level mitigations such as firewall rules to restrict access to the /api/webhook endpoint, particularly in environments where external access cannot be controlled. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and demonstrates how insufficient input validation can create exploitable conditions in continuous integration and deployment systems. The incident highlights the importance of implementing proper error handling and input validation in web services, especially those handling external integration points that are critical to business operations.