CVE-2018-10918 in Samba
Summary
by MITRE
A null pointer dereference flaw was found in the way samba checked database outputs from the LDB database layer. An authenticated attacker could use this flaw to crash a samba server in an Active Directory Domain Controller configuration. Samba versions before 4.7.9 and 4.8.4 are vulnerable.
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Analysis
by VulDB Data Team • 05/04/2023
The vulnerability identified as CVE-2018-10918 represents a critical null pointer dereference issue within the Samba implementation that specifically affects Active Directory Domain Controller configurations. This flaw exists in the database interaction layer where Samba processes outputs from the Lightweight Directory Access Protocol database layer known as LDB. The vulnerability stems from inadequate input validation and error handling within the authentication and database processing pathways that Samba employs when functioning as a domain controller. Attackers exploiting this weakness can leverage authenticated access to trigger a deliberate crash of the Samba server instance, effectively causing a denial of service condition that compromises the availability of directory services within the domain environment.
The technical exploitation of this vulnerability occurs when an authenticated attacker submits specific database query inputs that cause the LDB layer to return null values or unexpected database states. When Samba's processing logic attempts to dereference these null pointers without proper validation, the server crashes due to the unhandled exception. This type of flaw falls under CWE-476 which specifically addresses null pointer dereference conditions in software implementations. The vulnerability is particularly dangerous in Active Directory environments because it directly impacts the core functionality of domain controllers that rely on continuous availability of directory services for authentication, authorization, and resource access control across the network infrastructure.
The operational impact of CVE-2018-10918 extends beyond simple service disruption as it can severely compromise the integrity of domain authentication systems. In enterprise environments where Samba serves as a critical component of Active Directory integration, a successful exploitation can lead to unauthorized access to domain resources, disruption of authentication services, and potential lateral movement opportunities for attackers who might have already gained initial access. The vulnerability aligns with ATT&CK technique T1078 which covers legitimate credentials usage and can be leveraged as part of broader attack chains where initial access is followed by service disruption to maintain persistence or escalate privileges. The crash condition affects the availability of critical directory services that other systems depend upon for authentication and access control decisions.
Mitigation strategies for this vulnerability require immediate patching of affected Samba installations to versions 4.7.9 or 4.8.4 which contain the necessary code fixes to properly handle null pointer conditions in database interactions. System administrators should implement network segmentation and access controls to limit the scope of potential exploitation by restricting access to authenticated Samba services. Monitoring systems should be enhanced to detect unusual crash patterns or service disruptions in domain controller environments, particularly those involving database layer interactions. Additionally, implementing proper input validation and error handling procedures within custom Samba configurations can provide additional defense-in-depth measures. Organizations should also consider implementing intrusion detection systems that can identify anomalous database query patterns that might indicate exploitation attempts, while maintaining regular security assessments to identify similar vulnerabilities in other network services that might be susceptible to similar null pointer dereference conditions.