CVE-2015-6263 in IOS
Summary
by MITRE
The RADIUS client implementation in Cisco IOS 15.4(3)M2.2, when a shared RADIUS secret is configured, allows remote RADIUS servers to cause a denial of service (device reload) via malformed answers, aka Bug ID CSCuu59324.
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Analysis
by VulDB Data Team • 11/18/2024
The vulnerability described in CVE-2015-6263 represents a critical denial of service flaw within Cisco IOS RADIUS client implementations. This issue specifically affects Cisco IOS version 15.4(3)M2.2 and occurs when a shared RADIUS secret is configured on the device. The vulnerability stems from insufficient input validation in the RADIUS client processing logic, where malformed responses from remote RADIUS servers can trigger unexpected behavior in the underlying network infrastructure. The flaw operates at the authentication and authorization layer of network security, directly impacting the reliability and availability of network access control mechanisms.
The technical exploitation of this vulnerability occurs through carefully crafted malformed RADIUS responses that are sent by a malicious or compromised remote RADIUS server. When the affected Cisco IOS device receives such malformed answers, the RADIUS client implementation fails to properly handle the unexpected data structures, leading to a complete device reload or system crash. This behavior represents a classic buffer overflow or input validation failure scenario where the device's processing logic does not adequately sanitize incoming RADIUS packet contents before attempting to parse them. The vulnerability is particularly concerning because it requires no authentication or privileged access to exploit, making it accessible to any remote attacker who can establish communication with the target device.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network security posture and availability. Network administrators relying on RADIUS authentication for access control face significant risk as attackers could repeatedly exploit this vulnerability to cause persistent device reloads, effectively rendering network access controls unavailable. This denial of service condition undermines the fundamental security model of network infrastructure by preventing legitimate authentication requests from being processed, creating a window of vulnerability where unauthorized access attempts could potentially succeed. The vulnerability also impacts network monitoring and management systems that depend on continuous availability of authentication services, potentially causing cascading failures throughout the network infrastructure.
Mitigation strategies for CVE-2015-6263 should prioritize immediate patch application through official Cisco security advisories and firmware updates. Network administrators must implement network segmentation and access control measures to limit exposure of vulnerable devices to untrusted RADIUS servers, particularly in environments where multiple RADIUS servers are present. The implementation of RADIUS server authentication and certificate-based validation can provide additional layers of protection by ensuring that only authorized RADIUS servers can communicate with network devices. According to CWE classification, this vulnerability corresponds to CWE-121, which addresses buffer overflow conditions in stack-based buffers, and aligns with ATT&CK technique T1499.004 for network denial of service attacks. Organizations should also implement monitoring solutions to detect unusual RADIUS traffic patterns and device reload events that could indicate exploitation attempts, while maintaining detailed logs of authentication events for forensic analysis and incident response purposes.