CVE-2021-20179 in pki-core
Summary
by MITRE • 03/15/2021
A flaw was found in pki-core. An attacker who has successfully compromised a key could use this flaw to renew the corresponding certificate over and over again, as long as it is not explicitly revoked. The highest threat from this vulnerability is to data confidentiality and integrity.
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Analysis
by VulDB Data Team • 05/19/2025
This vulnerability exists within the pki-core component of a public key infrastructure system, representing a critical flaw in certificate lifecycle management that directly impacts the fundamental security guarantees of digital identity systems. The vulnerability allows an attacker who has already compromised a private key to repeatedly renew certificates associated with that key without explicit revocation, effectively bypassing the normal certificate validation mechanisms that should prevent such continuous renewal operations. This represents a significant weakening of the certificate-based trust model that underpins secure communications across networks and systems.
The technical implementation of this flaw stems from inadequate validation controls within the certificate renewal process, where the system fails to properly verify that a certificate can only be renewed a limited number of times or until its natural expiration. This weakness creates a persistent attack vector where compromised credentials can be indefinitely reused, undermining the principle of limited certificate validity periods that are essential for maintaining security boundaries. The vulnerability specifically affects the certificate renewal logic in the pki-core module, where proper authorization checks and state validation mechanisms are missing or insufficiently implemented, allowing unauthorized certificate extensions regardless of the certificate's actual status.
The operational impact of this vulnerability extends far beyond simple certificate management issues, as it fundamentally compromises the confidentiality and integrity of data protected by the compromised certificates. An attacker exploiting this flaw can maintain persistent access to encrypted systems and data, potentially intercepting communications and modifying information without detection, since the renewed certificates appear legitimate to systems that validate them. This vulnerability enables long-term surveillance and data manipulation attacks that can go undetected for extended periods, as the certificate renewal process appears normal to security monitoring systems that do not detect the unauthorized repeated extensions. The attack can be particularly devastating in environments where certificate-based authentication is used for critical infrastructure protection, financial transactions, or sensitive data handling.
Security mitigations for this vulnerability should focus on implementing robust certificate lifecycle management controls that enforce strict renewal limits and proper state tracking for all certificates within the pki-core system. Organizations must deploy enhanced monitoring solutions that can detect unusual certificate renewal patterns and establish automated alerting for certificates that are renewed beyond their expected limits. The fix requires implementing proper certificate state validation checks that prevent renewal operations when certificates have been compromised, along with strengthening the revocation checking mechanisms to ensure that renewed certificates cannot bypass the standard revocation processes. This vulnerability aligns with CWE-305 authentication bypass issues and maps to ATT&CK technique T1556.004 for credential access through certificate manipulation, emphasizing the need for comprehensive certificate management policies and continuous monitoring of certificate lifecycle events to prevent unauthorized certificate extensions.