CVE-2022-0336 in Samba
Summary
by MITRE • 08/29/2022
The Samba AD DC includes checks when adding service principals names (SPNs) to an account to ensure that SPNs do not alias with those already in the database. Some of these checks are able to be bypassed if an account modification re-adds an SPN that was previously present on that account, such as one added when a computer is joined to a domain. An attacker who has the ability to write to an account can exploit this to perform a denial-of-service attack by adding an SPN that matches an existing service. Additionally, an attacker who can intercept traffic can impersonate existing services, resulting in a loss of confidentiality and integrity.
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Analysis
by VulDB Data Team • 03/25/2026
The vulnerability identified as CVE-2022-0336 resides within the Samba Active Directory Domain Controller implementation, specifically affecting the service principal name (SPN) validation mechanisms. This flaw represents a critical security weakness in the directory service's account management functionality, where the system fails to properly enforce SPN uniqueness constraints during account modifications. The vulnerability stems from insufficient validation logic that allows attackers to bypass existing SPN aliasing checks through strategic account modification operations. When a computer joins a domain, it automatically receives certain SPNs, but the subsequent validation process becomes exploitable when an attacker can modify account attributes to reintroduce previously existing SPNs, creating a condition where the system's integrity checks are circumvented.
The technical exploitation of this vulnerability occurs through account modification operations that allow attackers with write permissions to an account to manipulate SPN attributes. The flaw specifically manifests when an attacker adds an SPN that matches an existing service principal name already present in the directory database, effectively creating a duplicate entry. This bypass mechanism operates because the validation logic does not adequately track or prevent re-addition of SPNs that were previously associated with an account, particularly those that were automatically added during domain join operations. The system's failure to maintain proper state tracking of SPN associations creates an opening for malicious actors to manipulate the directory service's authentication and authorization mechanisms.
The operational impact of CVE-2022-0336 extends beyond simple denial-of-service conditions to encompass significant confidentiality and integrity breaches. An attacker capable of performing account modifications can trigger denial-of-service attacks by introducing conflicting SPNs that disrupt legitimate service authentication processes. More critically, when attackers can intercept network traffic, they can exploit this vulnerability to impersonate existing services within the domain environment, effectively enabling man-in-the-middle attacks and credential theft operations. This capability directly violates the fundamental security principles of authentication and authorization, as the system's ability to distinguish between legitimate and malicious service principals becomes compromised, potentially allowing unauthorized access to sensitive domain resources.
The vulnerability aligns with CWE-306, which addresses "Missing Authentication for Critical Function," and represents a failure in proper access control validation within the Samba AD DC implementation. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and defense evasion, as attackers can leverage the SPN manipulation to gain unauthorized access while potentially evading detection through service impersonation. The exploitation path follows T1550.003, "Forge LLMNR/NBT-NS Responses," and T1071.004, "Application Layer Protocol: DNS," as attackers can manipulate service principal names to redirect authentication requests. Organizations should implement immediate mitigations including restricting write permissions to critical accounts, implementing enhanced monitoring for SPN modifications, and applying the latest security patches from Samba to address this validation bypass vulnerability.