A security flaw combining LDAP filter injection and improper authorization checks was found in Samba Active Directory Domain Controller (AD DC). When processing LDAP Compare requests, Samba fails to properly validate user-supplied attribute names and executes the resulting internal database search in a trusted context, bypassing normal Access Control List (ACL) enforcement. An authenticated low-privilege domain user can exploit these flaws to disclose confidential Active Directory attributes that would normally be inaccessible. The disclosed information may be leveraged to derive sensitive authentication material, potentially leading to privilege escalation and complete domain compromise. For example: In deployments configured with Group Managed Service Accounts (gMSAs), an attacker can extract the msKds-RootKeyData attribute and derive gMSA passwords offline, potentially leading to complete domain compromise if privileged gMSAs are present.
Weakness
The product constructs all or part of an LDAP query using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended LDAP query when it is sent to a downstream component.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Samba | Ubuntu | devel | * |
| Samba | Ubuntu | jammy | * |
| Samba | Ubuntu | noble | * |
| Samba | Ubuntu | resolute | * |
| Samba | Ubuntu | upstream | * |
Potential Mitigations
- Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
- When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
- Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.