CVE-2008-0948 in Kerberos
Summary
by MITRE
Buffer overflow in the RPC library (lib/rpc/rpc_dtablesize.c) used by libgssrpc and kadmind in MIT Kerberos 5 (krb5) 1.2.2, and probably other versions before 1.3, when running on systems whose unistd.h does not define the FD_SETSIZE macro, allows remote attackers to cause a denial of service (crash) and possibly execute arbitrary code by triggering a large number of open file descriptors.
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Analysis
by VulDB Data Team • 01/12/2025
The vulnerability described in CVE-2008-0948 represents a critical buffer overflow flaw within the Remote Procedure Call (RPC) library component of MIT Kerberos 5 version 1.2.2 and potentially earlier releases. This issue specifically affects systems where the unistd.h header file lacks the FD_SETSIZE macro definition, creating a dangerous condition that can be exploited by remote attackers to compromise system integrity. The vulnerability resides in the lib/rpc/rpc_dtablesize.c file, which is part of the libgssrpc and kadmind components of the Kerberos 5 suite, making it particularly concerning given Kerberos's widespread use in enterprise authentication systems.
The technical flaw manifests when the RPC library attempts to handle a large number of open file descriptors without proper bounds checking. In systems where FD_SETSIZE is not defined in unistd.h, the library defaults to an insufficient buffer size that cannot accommodate the actual number of file descriptors being processed. This buffer overflow condition occurs during the processing of RPC requests, where the system fails to validate the size of file descriptor sets before copying data into fixed-size buffers. The vulnerability is particularly dangerous because it can be triggered remotely through crafted RPC requests, allowing attackers to either crash the targeted service or potentially execute arbitrary code with the privileges of the affected process.
The operational impact of this vulnerability extends beyond simple denial of service, as it can lead to complete system compromise when exploited successfully. Attackers can leverage this weakness to cause crashes in critical Kerberos services such as kadmind (Kerberos administration daemon) and services utilizing libgssrpc, effectively disrupting authentication infrastructure. The potential for arbitrary code execution makes this vulnerability particularly attractive to malicious actors targeting enterprise networks that rely on Kerberos for authentication. Given that Kerberos is commonly deployed in mission-critical environments including financial institutions, government agencies, and large enterprises, the exploitation of this vulnerability could result in widespread service disruption and potential data breaches. The vulnerability affects systems where the RPC library is compiled without proper macro definitions, making it prevalent in certain Unix-like operating systems and their variants.
Mitigation strategies for CVE-2008-0948 primarily involve upgrading to MIT Kerberos 5 version 1.3 or later, which contains the necessary patches to address the buffer overflow condition. Organizations should also implement proper system configuration where FD_SETSIZE is appropriately defined in unistd.h or where the RPC library is compiled with sufficient buffer sizes to handle the expected number of file descriptors. Network segmentation and access controls should be implemented to limit exposure of vulnerable Kerberos services to untrusted networks. Additionally, monitoring systems should be configured to detect unusual patterns of RPC requests that might indicate exploitation attempts. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of improper input validation in system-level libraries. From an ATT&CK perspective, this vulnerability maps to techniques involving privilege escalation and denial of service, with potential for lateral movement through compromised Kerberos infrastructure. Organizations should conduct comprehensive vulnerability assessments to identify all systems running affected versions of MIT Kerberos and ensure proper patch management procedures are in place to prevent exploitation of this and similar legacy vulnerabilities.