CVE-2015-8631 in Kerberos
Summary
by MITRE
Multiple memory leaks in kadmin/server/server_stubs.c in kadmind in MIT Kerberos 5 (aka krb5) before 1.13.4 and 1.14.x before 1.14.1 allow remote authenticated users to cause a denial of service (memory consumption) via a request specifying a NULL principal name.
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Analysis
by VulDB Data Team • 07/07/2022
The vulnerability identified as CVE-2015-8631 represents a critical memory management flaw within the kadmind server component of MIT Kerberos 5 implementations. This issue affects versions prior to 1.13.4 and 1.14.1, specifically targeting the server_stubs.c file where the kadmin server processes authentication requests. The flaw manifests when remote authenticated users submit requests containing NULL principal names, creating a condition where memory allocated for processing these requests is not properly released back to the system. This memory leak occurs repeatedly with each malicious request, leading to progressive memory consumption that can eventually exhaust available system resources.
The technical root cause of this vulnerability lies in improper memory deallocation within the kadmin server stubs implementation. When processing authentication requests with NULL principal names, the server fails to correctly free allocated memory structures, resulting in memory leaks that accumulate over time. This represents a classic example of a resource leak vulnerability classified under CWE-404, which specifically addresses improper resource release or unmanaged resource consumption. The flaw exists in the server-side processing logic where input validation and memory management routines do not adequately handle edge cases involving null or malformed principal identifiers.
From an operational perspective, this vulnerability enables authenticated attackers to perform sustained denial of service attacks against Kerberos kadmin servers. The memory consumption grows progressively with each malicious request, potentially leading to system instability, service unavailability, and complete system crashes. Since the attack requires only authenticated access, it can be particularly dangerous in environments where authentication credentials are compromised or when attackers have legitimate access to the system. The impact extends beyond simple service disruption as the accumulated memory leaks can affect overall system performance and potentially cause cascading failures in dependent services that rely on the Kerberos infrastructure.
The vulnerability aligns with ATT&CK technique T1499.004, which covers "Resource Hijacking" through memory consumption attacks, and demonstrates how authenticated users can leverage legitimate system access to cause resource exhaustion. Organizations using MIT Kerberos 5 implementations should prioritize immediate patching of affected versions to address this vulnerability. The recommended mitigation strategy involves upgrading to krb5 versions 1.13.4 or 1.14.1 and later, which contain proper memory management fixes. Additionally, implementing monitoring systems to detect unusual memory consumption patterns on kadmin servers can provide early warning of potential exploitation attempts, while access controls and authentication auditing can help prevent unauthorized users from initiating these attacks.