CVE-2017-7177 in Suricata
Summary
by MITRE
Suricata before 3.2.1 has an IPv4 defragmentation evasion issue caused by lack of a check for the IP protocol during fragment matching.
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Analysis
by VulDB Data Team • 09/10/2020
The vulnerability identified as CVE-2017-7177 represents a critical flaw in the Suricata network intrusion detection system version 3.2.1 and earlier. This issue specifically affects the IPv4 defragmentation mechanism within the system, creating a potential pathway for attackers to evade detection by exploiting insufficient validation during the fragmentation process. The flaw stems from the absence of proper protocol checking during fragment matching operations, which allows malicious actors to craft packets that bypass normal inspection procedures.
The technical root cause of this vulnerability lies in the defragmentation logic that processes IPv4 fragments before reassembling them for inspection. During normal operation, Suricata should verify that all fragments belonging to a given IP packet belong to the same protocol type before attempting to reassemble them. However, the implementation failed to enforce this crucial validation step, enabling attackers to manipulate fragment ordering or protocol fields in ways that would normally trigger detection mechanisms. This oversight creates a condition where fragmented packets can be processed without proper protocol verification, allowing malicious payloads to slip through undetected.
From an operational perspective, this vulnerability significantly impacts network security monitoring capabilities by creating blind spots in the detection system. Attackers can exploit this flaw to craft evasion techniques that bypass signature-based and anomaly-based detection rules that rely on properly defragmented packets. The vulnerability is particularly dangerous because it operates at a fundamental level of packet processing, affecting the core functionality that enables network security appliances to inspect traffic for malicious content. This issue can be leveraged in various attack scenarios including stealthy malware delivery, command and control communication obfuscation, and other evasion techniques that rely on fragmented packet manipulation.
The impact of CVE-2017-7177 aligns with CWE-119 which addresses weaknesses in memory management and data handling, specifically concerning improper validation of data during processing. This vulnerability also maps to ATT&CK technique T1071.004 which covers application layer protocol: DNS, as attackers can exploit fragment evasion to bypass network monitoring systems that rely on proper defragmentation for protocol analysis. Organizations using Suricata for network security monitoring face significant risk exposure, as this flaw undermines the fundamental integrity of traffic inspection processes. The vulnerability demonstrates the critical importance of proper input validation and protocol consistency checks in security systems, particularly those handling network traffic processing.
Mitigation strategies for CVE-2017-7177 require immediate deployment of Suricata version 3.2.1 or later, which includes the necessary protocol validation fixes. Network administrators should also implement additional monitoring for unusual fragmentation patterns and establish baseline behavior for legitimate traffic to detect potential exploitation attempts. The fix addresses the core issue by implementing proper protocol field validation during fragment matching operations, ensuring that all fragments within a reassembly group belong to the same IP protocol before processing. Organizations should conduct thorough testing of updated systems to ensure that legitimate traffic processing remains unaffected while the vulnerability is resolved. This remediation effort should be part of broader network security hygiene practices that emphasize regular software updates and vulnerability management protocols.