CVE-2009-3111 in FreeRADIUS
Summary
by MITRE
The rad_decode function in FreeRADIUS before 1.1.8 allows remote attackers to cause a denial of service (radiusd crash) via zero-length Tunnel-Password attributes, as demonstrated by a certain module in VulnDisco Pack Professional 7.6 through 8.11. NOTE: this is a regression error related to CVE-2003-0967.
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Analysis
by VulDB Data Team • 02/27/2025
The vulnerability described in CVE-2009-3111 represents a critical denial of service flaw within the FreeRADIUS server implementation that affects versions prior to 1.1.8. This issue specifically targets the rad_decode function which processes RADIUS protocol attributes during authentication and authorization operations. The vulnerability emerged as a regression error, meaning it was reintroduced after a previous fix for CVE-2003-0967 had been implemented, demonstrating the complexity of maintaining security in network protocol implementations where seemingly minor changes can reintroduce exploitable conditions.
The technical flaw manifests when the rad_decode function encounters zero-length Tunnel-Password attributes within RADIUS packets. Tunnel-Password is a standard RADIUS attribute used for tunneling authentication information, typically containing encrypted passwords or authentication tokens that are essential for establishing secure network connections. When a malicious attacker crafts a RADIUS packet containing a Tunnel-Password attribute with a length of zero bytes, the function fails to properly handle this edge case, leading to a crash of the radiusd daemon process. This occurs because the decoding routine does not validate the attribute length before attempting to process its contents, creating a buffer over-read or improper memory access condition that ultimately results in the service termination.
The operational impact of this vulnerability extends beyond simple service disruption as it can be exploited by remote attackers without authentication, making it particularly dangerous in network environments where RADIUS servers handle critical authentication functions. The demonstration of this vulnerability through the VulnDisco Pack Professional 7.6 through 8.11 modules highlights how commercial security testing tools can be leveraged to exploit such flaws, potentially allowing attackers to systematically target network infrastructure. This type of denial of service attack can significantly impact network access control, potentially preventing legitimate users from accessing network resources while providing attackers with a means to disrupt network operations. The vulnerability particularly affects network environments that rely on FreeRADIUS for authentication, including wireless networks, VPN services, and enterprise authentication systems where RADIUS protocol compliance is essential.
The underlying issue aligns with CWE-129, which describes improper validation of array index or buffer length, and relates to the broader category of input validation failures that can lead to memory corruption vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and represents a critical weakness in the network infrastructure that can be exploited to disrupt authentication services. Organizations should implement immediate mitigations including upgrading to FreeRADIUS version 1.1.8 or later, where the vulnerability has been addressed through proper input validation of RADIUS attributes. Network segmentation and monitoring solutions can also help detect and prevent exploitation attempts, while regular security assessments should verify that all RADIUS implementations properly handle edge cases in attribute processing. The vulnerability serves as a reminder of the importance of thorough regression testing in security patches and the need for comprehensive input validation in protocol implementations that handle untrusted network data.