CVE-2012-1015 in Kerberos
Summary
by MITRE
The kdc_handle_protected_negotiation function in the Key Distribution Center (KDC) in MIT Kerberos 5 (aka krb5) 1.8.x, 1.9.x before 1.9.5, and 1.10.x before 1.10.3 attempts to calculate a checksum before verifying that the key type is appropriate for a checksum, which allows remote attackers to execute arbitrary code or cause a denial of service (uninitialized pointer free, heap memory corruption, and daemon crash) via a crafted AS-REQ request.
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Analysis
by VulDB Data Team • 03/27/2021
The vulnerability identified as CVE-2012-1015 resides within the Key Distribution Center (KDC) component of MIT Kerberos 5, specifically in the kdc_handle_protected_negotiation function. This flaw affects versions 1.8.x, 1.9.x before 1.9.5, and 1.10.x before 1.10.3, representing a critical security weakness that undermines the integrity of the Kerberos authentication system. The vulnerability stems from improper validation of cryptographic key types during the authentication process, creating a scenario where malicious actors can exploit the system's handling of checksum calculations.
The technical flaw manifests when the KDC processes an AS-REQ (Authentication Service Request) message containing crafted parameters. The function attempts to compute a checksum before performing essential validation checks to ensure that the key type specified in the request is compatible with the checksum algorithm being applied. This premature checksum calculation results in a race condition where memory operations occur without proper initialization verification. The vulnerability falls under CWE-457, which describes "Use of Uninitialized Variable," and more specifically relates to CWE-125, "Out-of-bounds Read," and CWE-787, "Out-of-bounds Write," as the uninitialized memory access can lead to heap corruption.
Attackers can leverage this vulnerability through carefully constructed AS-REQ requests that manipulate the key type field to trigger the flawed code path. The exploitation consequences include arbitrary code execution, denial of service through daemon crashes, and heap memory corruption that can compromise the entire authentication infrastructure. This represents a significant threat to systems relying on Kerberos for authentication, as successful exploitation can allow attackers to bypass authentication mechanisms or disrupt services entirely. The vulnerability aligns with ATT&CK technique T1550.003, "Use of Kerberos," and T1499.004, "Endpoint Denial of Service," demonstrating how authentication system weaknesses can be weaponized for both privilege escalation and service disruption.
The operational impact extends beyond immediate exploitation capabilities to encompass broader security implications for organizations using Kerberos-based authentication. Systems that depend on Kerberos for single sign-on, service authentication, and cross-domain authentication become vulnerable to attacks that can compromise user credentials and service availability. Organizations must consider the cascading effects of such vulnerabilities, as they can undermine trust in the entire authentication ecosystem and potentially enable lateral movement within networks. The vulnerability affects the core authentication process, making it particularly dangerous as it can be exploited without requiring prior access to the system.
Mitigation strategies should focus on immediate patching of affected Kerberos versions to the patched releases 1.9.5 and 1.10.3, respectively, which address the improper validation of key types before checksum calculation. Network segmentation and monitoring of Kerberos traffic can provide additional defense-in-depth measures, allowing administrators to detect anomalous AS-REQ patterns that might indicate exploitation attempts. Implementing proper input validation and ensuring that all cryptographic operations verify key type compatibility before performing calculations can prevent similar vulnerabilities in other components. Security teams should also consider implementing intrusion detection systems specifically configured to monitor for Kerberos protocol anomalies and establish incident response procedures that address authentication system compromises. The vulnerability highlights the importance of proper resource management and validation in cryptographic implementations, emphasizing that security-critical functions must validate all inputs before performing sensitive operations.