CVE-2017-15088 in Kerberos 5
Summary
by MITRE
plugins/preauth/pkinit/pkinit_crypto_openssl.c in MIT Kerberos 5 (aka krb5) through 1.15.2 mishandles Distinguished Name (DN) fields, which allows remote attackers to execute arbitrary code or cause a denial of service (buffer overflow and application crash) in situations involving untrusted X.509 data, related to the get_matching_data and X509_NAME_oneline_ex functions. NOTE: this has security relevance only in use cases outside of the MIT Kerberos distribution, e.g., the use of get_matching_data in KDC certauth plugin code that is specific to Red Hat.
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Analysis
by VulDB Data Team • 01/16/2023
The vulnerability CVE-2017-15088 represents a critical buffer overflow flaw within the MIT Kerberos 5 implementation that specifically targets the handling of Distinguished Name fields in X.509 certificates. This issue exists in the pkinit_crypto_openssl.c file and affects versions through 1.15.2, making it a persistent threat across multiple releases of the widely-used authentication system. The vulnerability stems from improper validation and processing of X.509 certificate data, particularly when the system encounters untrusted certificate information during the Kerberos pre-authentication process. The flaw manifests through the get_matching_data and X509_NAME_oneline_ex functions, which are critical components in the certificate validation workflow of the Kerberos infrastructure.
The technical exploitation of this vulnerability occurs when the Kerberos Key Distribution Center processes X.509 certificates containing malformed Distinguished Name fields. The buffer overflow vulnerability arises from insufficient bounds checking when processing certificate data, allowing attackers to craft specially crafted certificates that trigger memory corruption. This flaw operates at the cryptographic layer where Kerberos performs certificate authentication, specifically within the KDC certauth plugin code that is implemented in Red Hat distributions. The vulnerability's impact extends beyond simple denial of service to potentially enable arbitrary code execution, making it particularly dangerous in environments where Kerberos is used for critical authentication services. The issue demonstrates a classic CWE-121 buffer overflow condition where insufficient input validation leads to memory corruption.
From an operational perspective, this vulnerability creates significant security risks for organizations relying on Kerberos authentication systems, particularly those using Red Hat implementations where the KDC certauth plugin code is present. The attack vector requires remote access to the Kerberos infrastructure, making it accessible to attackers who can submit malicious certificates to the authentication system. The potential for arbitrary code execution means that successful exploitation could lead to complete system compromise, allowing attackers to escalate privileges and gain unauthorized access to protected resources. Organizations using MIT Kerberos in environments where certificate-based authentication is enabled face the highest risk, especially in scenarios involving cross-domain trust relationships or federation scenarios where external certificates are processed. The vulnerability's relevance is further emphasized by its specific targeting of Red Hat implementations, suggesting that organizations using these distributions may have additional exposure.
Mitigation strategies for CVE-2017-15088 should focus on immediate patching of affected MIT Kerberos installations, particularly versions through 1.15.2, to address the buffer overflow in certificate processing functions. Organizations should also implement network segmentation and access controls to limit exposure of Kerberos services to untrusted certificate sources, reducing the attack surface for this vulnerability. Additional defensive measures include monitoring for anomalous certificate processing patterns and implementing certificate validation policies that restrict the types of certificates accepted by Kerberos systems. The vulnerability's classification under ATT&CK technique T1552.001 (Credentials in Files) highlights the importance of securing certificate storage and processing environments, while its relationship to CWE-121 emphasizes the need for robust input validation mechanisms. Security teams should also consider implementing intrusion detection systems that can identify attempts to exploit buffer overflow conditions in authentication infrastructure, as the vulnerability's exploitation may generate detectable network traffic patterns or system behavior anomalies.