CVE-2026-91923 in KubeSphere
Summary
by MITRE • 09/15/2026
KubeSphere through 4.1.3 contains a server-side request forgery vulnerability in the git credential verification endpoint that accepts unvalidated caller-supplied URLs without allowlist restrictions. Authenticated attackers can supply arbitrary URLs to reach internal services and exfiltrate basic-auth credentials from Secrets in any namespace by leveraging the endpoint's error response handling.
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Analysis
by VulDB Data Team • 09/15/2026
The identified security flaw resides within KubeSphere versions up to 4.1.3, specifically affecting the git credential verification endpoint which is designed to validate external repository connectivity for continuous integration and deployment workflows. This component suffers from a Server-Side Request Forgery vulnerability due to insufficient input validation on URLs provided by authenticated users. The system fails to enforce an allowlist of permitted domains or IP ranges, allowing attackers to supply arbitrary Uniform Resource Locators that the backend service will subsequently request. This architectural oversight transforms a standard authentication mechanism into a vector for internal network reconnaissance and data exfiltration, as the application acts as a proxy for HTTP requests without restricting the destination scope.
From an operational perspective, this vulnerability allows authenticated adversaries to pivot from user-level access to deeper infrastructure compromise. By crafting malicious payloads that target internal Kubernetes services or metadata endpoints, attackers can probe the internal network topology and identify sensitive resources. The most critical impact involves the exfiltration of basic-auth credentials stored within Kubernetes Secrets across any namespace accessible to the attacker. Because the error response handling mechanism leaks information about the request outcome, it provides a reliable oracle for blind SSRF attacks. Attackers can leverage timing differences or specific error messages to confirm successful connections and extract sensitive data that would otherwise remain isolated from external access paths.
This vulnerability aligns with Common Weakness Enumeration CWE-918, which classifies Server-Side Request Forgery as a critical design flaw where the web server retrieves a specified resource without validating user-supplied URLs. Furthermore, the exploitation technique maps to MITRE ATT&CK tactic T1557, specifically Adversary-in-the-Middle or Lateral Tool Transfer scenarios where internal services are abused for data staging and exfiltration. The ability to access Secrets in any namespace indicates a failure in namespace isolation principles, potentially violating CIS Kubernetes Benchmark recommendations regarding strict RBAC policies and secret management protocols.
To mitigate this risk, immediate remediation should involve upgrading KubeSphere to version 4.1.3 or later where the vulnerability has been addressed through enhanced input validation mechanisms. Administrators must implement strict allowlists for permitted domains in any git integration endpoints that accept external URLs. Additionally, network-level controls such as egress filtering and firewall rules restricting outbound traffic from application pods should be enforced to prevent access to internal metadata services like 169.254.169.254 or cluster-internal service IPs. Monitoring logs for unusual HTTP request patterns originating from the git credential verification endpoint can also aid in early detection of exploitation attempts before significant data loss occurs.