CVE-2015-8629 in Kerberos
Summary
by MITRE
The xdr_nullstring function in lib/kadm5/kadm_rpc_xdr.c in kadmind in MIT Kerberos 5 (aka krb5) before 1.13.4 and 1.14.x before 1.14.1 does not verify whether '\0' characters exist as expected, which allows remote authenticated users to obtain sensitive information or cause a denial of service (out-of-bounds read) via a crafted string.
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Analysis
by VulDB Data Team • 07/07/2022
The CVE-2015-8629 vulnerability resides within the xdr_nullstring function implementation in MIT Kerberos 5's kadmind service, specifically in the lib/kadm5/kadm_rpc_xdr.c file. This flaw affects versions prior to 1.13.4 and 1.14.1, representing a critical security weakness in the Kerberos authentication system that underpins many enterprise security infrastructures. The vulnerability manifests when the function fails to properly validate null character sequences within strings, creating a potential attack surface for authenticated remote adversaries seeking to exploit the system's handling of serialized data.
The technical implementation of this vulnerability stems from improper bounds checking during XDR (External Data Representation) string processing. When kadmind receives RPC requests containing crafted strings, the xdr_nullstring function does not adequately verify the presence of null terminators as expected in the data format. This oversight allows attackers to manipulate string boundaries in ways that can trigger out-of-bounds memory reads, potentially exposing sensitive information from adjacent memory locations or causing system crashes through denial of service conditions. The flaw operates at the protocol level where Kerberos administrative services communicate, making it particularly dangerous for systems relying on centralized authentication management.
Operational impact of this vulnerability extends beyond simple denial of service scenarios to include potential information disclosure risks that could compromise entire authentication domains. An authenticated attacker with access to the kadmind service can exploit this weakness to read memory contents that may contain cryptographic keys, user credentials, or other sensitive administrative data. The vulnerability's presence in the Kerberos administration daemon means that successful exploitation could provide attackers with elevated privileges within the authentication infrastructure, potentially enabling lateral movement and further compromise of network resources. The out-of-bounds read conditions can also cause system instability, leading to service disruption that affects legitimate authentication requests and potentially creating denial of service scenarios for authorized users.
Mitigation strategies for CVE-2015-8629 primarily involve upgrading to patched versions of MIT Kerberos 5, specifically versions 1.13.4 or 1.14.1 and later. System administrators should prioritize patching all instances of kadmind services, particularly those handling administrative functions for Kerberos realms. Network segmentation and access controls should be implemented to limit exposure of kadmind services to only trusted administrative networks. Monitoring for unusual RPC traffic patterns and implementing intrusion detection systems can help identify potential exploitation attempts. Additionally, organizations should conduct thorough security assessments of their Kerberos implementations to identify any other potential vulnerabilities in the authentication infrastructure. This vulnerability aligns with CWE-129, which addresses improper validation of array indices, and may map to ATT&CK technique T1552 for credential access and T1499 for endpoint denial of service, emphasizing the multi-faceted nature of the threat landscape.