CVE-2016-10396 in Ipsec-tools
Summary
by MITRE
The racoon daemon in IPsec-Tools 0.8.2 contains a remotely exploitable computational-complexity attack when parsing and storing ISAKMP fragments. The implementation permits a remote attacker to exhaust computational resources on the remote endpoint by repeatedly sending ISAKMP fragment packets in a particular order such that the worst-case computational complexity is realized in the algorithm utilized to determine if reassembly of the fragments can take place.
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Analysis
by VulDB Data Team • 10/23/2019
The CVE-2016-10396 vulnerability resides within the racoon daemon component of IPsec-Tools version 0.8.2, representing a significant computational complexity attack that targets the Internet Security Association and Key Management Protocol implementation. This flaw specifically manifests during the processing of ISAKMP (Internet Security Association and Key Management Protocol) fragment packets, which are essential for establishing secure IPsec connections. The vulnerability exploits a weakness in how the daemon handles fragment reassembly, creating a scenario where an attacker can deliberately trigger worst-case algorithmic behavior through carefully crafted packet sequences.
The technical implementation of this vulnerability stems from inefficient fragment reassembly algorithms that do not properly account for computational complexity bounds during packet processing. When the racoon daemon receives ISAKMP fragment packets, it must determine whether the fragments can be successfully reassembled into a complete message. The flawed implementation lacks proper input validation and complexity bounds checking, allowing an attacker to construct fragment sequences that force the daemon to perform excessive computational work. This results in a denial-of-service condition where the system's resources become consumed through repeated processing of these maliciously crafted fragments.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a sophisticated resource exhaustion attack that can be executed remotely without authentication. Attackers can leverage this vulnerability to consume CPU cycles, memory, and other system resources until the target system becomes unresponsive or crashes entirely. The attack is particularly concerning because it can be executed against systems running IPsec implementations that rely on the racoon daemon for key exchange operations, potentially affecting network infrastructure, firewalls, and other security appliances that implement IPsec protocols. This vulnerability directly maps to CWE-778 (Insufficient Logging) and CWE-400 (Uncontrolled Resource Consumption) categories, as the implementation fails to properly manage resource allocation during fragment processing.
Mitigation strategies for this vulnerability require immediate patching of IPsec-Tools installations to version 0.8.3 or later, which contains the necessary algorithmic improvements and complexity bounds checking. Network administrators should also implement rate limiting and fragment filtering mechanisms at network boundaries to prevent excessive fragment processing. The remediation approach aligns with ATT&CK technique T1499.004 (Endpoint Denial of Service) and emphasizes the importance of proper algorithmic complexity management in security-critical systems. Additionally, organizations should consider implementing monitoring solutions to detect unusual patterns of fragment processing that might indicate exploitation attempts, while ensuring that all IPsec implementations undergo thorough security testing for computational complexity vulnerabilities.