CVE-2007-4000 in Kerberos
Summary
by MITRE
The kadm5_modify_policy_internal function in lib/kadm5/srv/svr_policy.c in the Kerberos administration daemon (kadmind) in MIT Kerberos 5 (krb5) 1.5 through 1.6.2 does not properly check return values when the policy does not exist, which might allow remote authenticated users with the "modify policy" privilege to execute arbitrary code via unspecified vectors that trigger a write to an uninitialized pointer.
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Analysis
by VulDB Data Team • 01/11/2025
The vulnerability identified as CVE-2007-4000 resides within the Kerberos administration daemon kadmind in MIT Kerberos 5 versions 1.5 through 1.6.2. This flaw specifically affects the kadm5_modify_policy_internal function located in lib/kadm5/srv/svr_policy.c, representing a critical security weakness that could enable remote authenticated attackers to achieve arbitrary code execution. The vulnerability stems from inadequate error handling mechanisms within the policy modification process, creating a scenario where the system fails to properly validate the existence of policies before attempting to modify them.
The technical root cause of this vulnerability manifests as a failure to properly check return values when attempting to modify non-existent policies. When an authenticated user with appropriate privileges attempts to modify a policy that does not exist, the function does not adequately validate the operation's success or failure status. This oversight creates a condition where the system continues execution without proper initialization of required memory structures, leading to a write operation against an uninitialized pointer. Such pointer dereferencing errors represent classic software vulnerabilities that can be exploited to gain control over the targeted system.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with a pathway to achieve arbitrary code execution within the kadmind daemon process. This represents a severe security compromise since kadmind operates with elevated privileges and manages critical authentication infrastructure. Attackers could leverage this vulnerability to execute malicious code with the same privileges as the kadmind service, potentially allowing them to manipulate Kerberos policy settings, access sensitive authentication data, or even establish persistent access to the authentication infrastructure. The vulnerability is particularly dangerous because it requires only authenticated access with specific privileges, making it exploitable by users who already have legitimate access to the Kerberos administration interface.
This vulnerability aligns with CWE-476, which describes NULL pointer dereference conditions that can lead to arbitrary code execution. The flaw also maps to ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' and T1548.001, covering 'Abuse Elevation Control Mechanism'. Organizations using affected MIT Kerberos versions face significant risk, as the vulnerability allows attackers to bypass normal access controls and execute code within the privileged context of the administration daemon. The exploitation requires minimal privileges beyond authentication, making it particularly attractive to threat actors seeking to compromise authentication infrastructure. The vulnerability demonstrates the critical importance of proper error handling and input validation in security-critical components, as inadequate validation can create pathways for privilege escalation and arbitrary code execution.
Mitigation strategies for this vulnerability include immediate patching of affected MIT Kerberos installations to versions that address the flawed error handling in the kadm5_modify_policy_internal function. Organizations should also implement network segmentation to limit access to kadmind services, restrict authentication privileges to only necessary users, and monitor for unusual policy modification activities. Additionally, implementing intrusion detection systems that can identify potential exploitation attempts and maintaining up-to-date security monitoring of authentication infrastructure will help detect and respond to exploitation attempts. The vulnerability serves as a reminder of the critical need for thorough error handling in security-sensitive code and demonstrates how seemingly minor validation flaws can result in major security compromises.