CVE-2003-0968 in FreeRADIUS
Summary
by MITRE
Stack-based buffer overflow in SMB_Logon_Server of the rlm_smb experimental module for FreeRADIUS 0.9.3 and earlier allows remote attackers to execute arbitrary code via a long User-Password attribute.
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Analysis
by VulDB Data Team • 07/04/2017
The vulnerability identified as CVE-2003-0968 represents a critical stack-based buffer overflow flaw within the rlm_smb experimental module of FreeRADIUS version 0.9.3 and earlier. This issue specifically affects the SMB_Logon_Server function which processes authentication requests through the SMB protocol. The vulnerability arises from insufficient input validation when handling the User-Password attribute, a standard component in authentication protocols that carries credential information from clients to authentication servers. The flaw exists in the experimental rlm_smb module which provides SMB authentication capabilities for the FreeRADIUS server, making it particularly concerning as it affects a core authentication mechanism used in network access control systems.
The technical implementation of this vulnerability stems from improper bounds checking within the SMB_Logon_Server function. When processing authentication requests, the module fails to validate the length of the User-Password attribute before copying it into a fixed-size stack buffer. This allows an attacker to supply a User-Password attribute that exceeds the allocated buffer space, causing a stack overflow condition. The overflow occurs because the module uses a vulnerable copying mechanism that does not perform adequate size verification before memory operations. This type of vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue that can lead to arbitrary code execution. The attack vector is remote, meaning an attacker can exploit this vulnerability without requiring physical access to the system, making it particularly dangerous in networked environments where FreeRADIUS servers are exposed to external traffic.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with complete control over the affected FreeRADIUS server. Successful exploitation allows remote code execution with the privileges of the FreeRADIUS service account, which typically runs with elevated system permissions. This compromise can lead to unauthorized network access, credential theft, and potential lateral movement within the network infrastructure. The vulnerability affects organizations that rely on FreeRADIUS for network access control, particularly those implementing SMB-based authentication mechanisms. Given that FreeRADIUS is commonly deployed in enterprise environments for wireless network access, VPN authentication, and other network security services, the potential for widespread impact is significant. The experimental nature of the rlm_smb module means that administrators may not have fully considered its security implications, making this vulnerability particularly dangerous as it may remain undetected for extended periods.
Mitigation strategies for CVE-2003-0968 should focus on immediate patching of the FreeRADIUS software to version 0.9.4 or later where the vulnerability has been resolved through proper input validation and buffer management. Organizations should also consider disabling the experimental rlm_smb module if SMB authentication is not critical to their operations, as this eliminates the attack surface entirely. Network segmentation and access controls should be implemented to limit exposure of FreeRADIUS servers to untrusted networks. Security monitoring should include detection of unusual authentication patterns and potential exploitation attempts targeting the vulnerable module. The ATT&CK framework categorizes this vulnerability under T1110 Brute Force and T1078 Valid Accounts, as attackers may leverage this vulnerability to establish persistent access through compromised authentication systems. Additionally, organizations should implement regular security assessments to identify and remediate experimental or deprecated modules that may contain unpatched vulnerabilities, as the rlm_smb module's experimental status indicates potential security gaps that may not be adequately addressed in standard security reviews.