CVE-2026-104988 in Certificate System
Summary
by MITRE • 10/02/2026
A flaw was found in Dogtag PKI (pki-core). The CMCAuthForEST authentication plugin fails open when an EST fullcmc enrollment request is submitted via BasicAuth without an end-user TLS client certificate. The SSL_CLIENT_CERT session attribute retains the EST subsystem's agent certificate, which causes downstream authorization checks to treat the request as agent-privileged. An authenticated EST user can exploit this to obtain CA-signed certificates with arbitrary subject names.
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Analysis
by VulDB Data Team • 10/02/2026
The vulnerability identified in Dogtag PKI within the pki-core component represents a critical authentication bypass mechanism rooted in the improper handling of client certificate attributes during Extended Certificate Signing Request (EST) operations. Specifically, the CMCAuthForEST authentication plugin exhibits an open authorization flaw when processing full CA enrollment requests that utilize Basic Authentication without providing a corresponding end-user TLS client certificate. In standard PKI workflows, EST is designed to facilitate automated certificate management by allowing devices or users to enroll for certificates securely. However, in this specific scenario, the system fails to enforce the requirement of a valid end-entity certificate when Basic Auth is employed as the primary authentication method. Instead of rejecting the request due to missing client credentials, the underlying SSL context retains the session attribute SSL_CLIENT_CERT populated with the EST subsystem's own agent certificate rather than an empty or null value indicating no client cert was presented.
This technical flaw leads directly to a severe authorization bypass because downstream components rely on the presence and content of the SSL_CLIENT_CERT attribute to determine the privilege level of the requester. Since the session retains the agent certificate, the system incorrectly interprets the incoming request as being authenticated with elevated privileges associated with that agent identity. Consequently, an attacker who has obtained valid Basic Authentication credentials for a standard EST user can exploit this discrepancy to impersonate higher-privileged entities or bypass restrictions intended only for administrative agents. The core issue lies in the failure of the authentication plugin to validate that the certificate presented during the TLS handshake matches the identity asserted by the Basic Auth credentials, and more critically, its failure to clear or properly handle the agent certificate when no end-user certificate is provided.
The operational impact of this vulnerability is significant, as it allows an authenticated EST user to obtain Certificate Authority-signed certificates with arbitrary subject names. This capability undermines the fundamental trust model of a Public Key Infrastructure. By obtaining certificates with arbitrary subjects, an attacker can create valid identities for any domain, service account, or individual within the organization's scope. These forged certificates can then be used for man-in-the-middle attacks, unauthorized access to internal services that rely on mutual TLS authentication, or spoofing legitimate entities in email and code signing scenarios. The ability to generate arbitrary subject names means there is no restriction preventing the creation of certificates that appear identical to those issued to critical infrastructure components or high-privilege accounts, thereby facilitating lateral movement and persistent access within a compromised network environment.
From a classification perspective, this vulnerability aligns with CWE-287 Improper Authentication, as the system fails to correctly verify the identity of the user during the authentication process due to flawed logic in handling TLS client certificates alongside Basic Auth. It also relates closely to CWE-862 Missing Authorization Check, since the downstream authorization checks are misled by the retained agent certificate attribute, effectively granting privileges that were not intended for the requesting entity. In terms of MITRE ATT&CK mapping, this exploit technique corresponds to T1078 Valid Accounts and potentially T1550 Use Alternate Authentication Material, as it involves leveraging valid credentials but manipulating the authentication context to gain unauthorized access or impersonation capabilities.
Mitigation strategies must focus on correcting the logic within the CMCAuthForEST plugin to ensure strict validation of client certificates when required by the enrollment type. Administrators should apply vendor-provided patches that address this specific flaw in pki-core, ensuring that the SSL_CLIENT_CERT attribute is properly cleared or validated against the expected end-user identity before proceeding with authorization checks. Additionally, organizations relying on Dogtag PKI for EST operations should review their configuration to ensure that Basic Authentication without client certificates is disabled if not strictly necessary, thereby reducing the attack surface. Implementing strict certificate pinning and monitoring logs for unusual enrollment patterns involving arbitrary subject names can also help in detecting potential exploitation attempts before they result in significant compromise of the PKI trust chain.