CVE-2004-0808 in Samba
Summary
by MITRE
The process_logon_packet function in the nmbd server for Samba 3.0.6 and earlier, when domain logons are enabled, allows remote attackers to cause a denial of service via a SAM_UAS_CHANGE request with a length value that is larger than the number of structures that are provided.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 07/07/2025
The vulnerability described in CVE-2004-0808 affects the nmbd server component within Samba versions 3.0.6 and earlier, specifically when domain logons are enabled. This represents a critical denial of service weakness that exploits a fundamental flaw in how the server processes authentication requests. The nmbd daemon serves as the NetBIOS name server and messenger service within Samba, handling network name resolution and message passing between Windows clients and servers. When domain logons are enabled, the system must process SAM_UAS_CHANGE requests which are part of the Windows authentication protocol for managing user accounts and password changes. The vulnerability stems from inadequate input validation within the process_logon_packet function, which fails to properly validate the length parameter in these requests before processing them.
The technical flaw manifests when a remote attacker crafts a malicious SAM_UAS_CHANGE request with a length value that exceeds the actual number of structures provided in the payload. This discrepancy creates a buffer overflow condition or memory corruption scenario within the nmbd server process, causing the service to crash or become unresponsive. The vulnerability specifically targets the protocol handling layer rather than the application itself, making it particularly dangerous as it can be exploited without requiring authentication or elevated privileges. The attack vector operates over the network, allowing an unauthenticated remote attacker to disrupt service availability by simply sending a malformed request to the vulnerable Samba server.
The operational impact of this vulnerability extends beyond simple service disruption, as it can effectively render the entire Samba domain logon functionality unusable. When the nmbd server crashes due to this flaw, it affects not only the immediate authentication capabilities but also the broader network name resolution services that depend on this component. Organizations relying on Samba for Windows domain integration face significant operational risks, as the service disruption can cascade to affect file sharing, printer services, and other network resources that depend on proper name resolution. The vulnerability's exploitation requires minimal technical skill, making it particularly dangerous in environments where network monitoring is insufficient or where attackers may be actively targeting Samba implementations.
Mitigation strategies for CVE-2004-0808 primarily focus on immediate patching of the affected Samba versions, with the vulnerability being resolved in Samba 3.0.7 and subsequent releases. Organizations should implement network segmentation to limit exposure of vulnerable Samba servers to untrusted networks, while also deploying intrusion detection systems that can identify suspicious SAM_UAS_CHANGE requests. The fix implemented by Samba developers involved adding proper bounds checking to validate the length parameter against the actual structure count in incoming requests, preventing the buffer overflow condition. Security monitoring should include logging of authentication-related traffic patterns and implementing rate limiting to prevent abuse of the vulnerable function. This vulnerability aligns with CWE-129, which describes improper validation of length parameters, and maps to ATT&CK technique T1499.004 for denial of service attacks targeting network services. Organizations should also consider implementing network access controls to restrict access to Samba services from trusted networks only, reducing the attack surface for this and similar vulnerabilities.