CVE-2017-10985 in FreeRADIUS
Summary
by MITRE
An FR-GV-302 issue in FreeRADIUS 3.x before 3.0.15 allows "Infinite loop and memory exhaustion with 'concat' attributes" and a denial of service.
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Analysis
by VulDB Data Team • 12/13/2022
The vulnerability identified as CVE-2017-10985 represents a critical denial of service weakness within the FreeRADIUS authentication server software. This issue specifically affects versions 3.x prior to 3.0.15 and stems from improper handling of 'concat' attributes within the server's processing logic. The flaw manifests when the server encounters certain malformed or maliciously constructed configuration files that contain concat attributes, leading to unintended behavior during attribute processing. The vulnerability operates through a specific code path where the server's attribute handling mechanism fails to properly validate or limit the recursive processing of concatenated attribute values, creating a condition where the processing loop can become infinite. This infinite loop condition directly translates into memory exhaustion as the server continuously allocates memory resources without proper termination conditions, ultimately causing the system to become unresponsive and unable to process legitimate authentication requests.
The technical implementation of this vulnerability aligns with CWE-835, which describes the weakness of an infinite loop without a valid exit condition. In the context of FreeRADIUS, this manifests when the server attempts to process attribute values that contain recursive concatenation patterns that cannot be properly resolved or terminated. The attacker can exploit this by crafting specific configuration files or authentication requests that contain malformed concat attributes, causing the server to enter an infinite processing loop. The operational impact extends beyond simple service disruption as the memory exhaustion component can cause the entire system to become unstable, potentially leading to system crashes or requiring manual intervention to restore normal operations. This vulnerability particularly affects network infrastructure components that rely on FreeRADIUS for authentication services, including wireless access points, VPN servers, and network access control systems that depend on the server's ability to process authentication attributes correctly.
From an attack perspective, this vulnerability maps to several ATT&CK techniques including TA0043 (Reconnaissance) where adversaries might identify vulnerable FreeRADIUS installations, and TA0040 (Defense Evasion) through the use of denial of service attacks to disrupt legitimate network access. The exploitability of this vulnerability is relatively straightforward as it requires only the ability to influence the configuration of the FreeRADIUS server or submit specially crafted authentication requests that contain malicious concat attributes. Organizations running FreeRADIUS versions prior to 3.0.15 face significant risk as this vulnerability can be leveraged to create persistent denial of service conditions that may be difficult to detect and remediate. The memory exhaustion aspect of the vulnerability means that even a single malicious request can consume substantial system resources, potentially affecting multiple concurrent authentication requests and creating cascading failures within network access control systems that depend on the server's availability.
The recommended mitigation strategy involves immediate upgrading to FreeRADIUS version 3.0.15 or later, which contains the necessary patches to properly validate and limit recursive attribute processing. Organizations should also implement monitoring solutions that can detect unusual memory consumption patterns or processing loops within their FreeRADIUS instances. Configuration hardening measures should include validating all attribute values and implementing rate limiting for authentication requests to prevent abuse of the vulnerable code path. Network segmentation and access controls should be implemented to limit exposure of FreeRADIUS servers to untrusted networks, reducing the attack surface for this type of vulnerability. Additionally, regular security assessments and vulnerability scanning should be conducted to identify any other potential weaknesses in the authentication infrastructure that could be exploited in conjunction with this denial of service vulnerability.