CVE-2017-15377 in Suricata
Summary
by MITRE
In Suricata before 4.x, it was possible to trigger lots of redundant checks on the content of crafted network traffic with a certain signature, because of DetectEngineContentInspection in detect-engine-content-inspection.c. The search engine doesn't stop when it should after no match is found; instead, it stops only upon reaching inspection-recursion-limit (3000 by default).
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Analysis
by VulDB Data Team • 01/04/2023
The vulnerability identified as CVE-2017-15377 represents a significant performance degradation issue within the Suricata network intrusion detection system prior to version 4.x. This flaw exists in the content inspection mechanism of the detection engine, specifically within the detect-engine-content-inspection.c module where the search engine fails to terminate its inspection process appropriately when no matches are found. The issue stems from the detection engine's inability to properly manage its inspection recursion limits, leading to excessive computational overhead during signature processing.
The technical flaw manifests when crafted network traffic is processed through Suricata's signature matching system, particularly with specific content-based signatures that trigger redundant inspection checks. The detection engine employs a search algorithm that continues processing even after determining that no matches exist, rather than terminating the inspection cycle as it should. This behavior is governed by the inspection-recursion-limit parameter which defaults to 3000 iterations, meaning that the engine will continue checking content patterns until it reaches this arbitrary limit regardless of whether matches have been found or not. This inefficient handling directly violates the expected behavior of content search algorithms and represents a deviation from proper algorithmic termination conditions.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially enable denial-of-service conditions within network monitoring environments. When processing maliciously crafted traffic, an attacker could construct packets designed to trigger the redundant inspection behavior, causing Suricata to consume excessive CPU cycles and memory resources. This could lead to system slowdowns, complete service unavailability, or even system crashes depending on the scale and frequency of such attacks. The vulnerability particularly affects environments where Suricata processes high volumes of network traffic or where signature-based detection is heavily utilized, making it a critical concern for network security operations centers that rely on continuous monitoring.
The flaw aligns with CWE-400, which addresses unchecked resource consumption, and demonstrates poor resource management practices in the detection engine's content inspection routines. From an attack perspective, this vulnerability maps to the ATT&CK technique T1499.004, specifically targeting network denial-of-service conditions through resource exhaustion. The vulnerability essentially allows an attacker to consume system resources without meaningful detection, creating a scenario where legitimate network monitoring operations become impaired. Organizations should implement immediate mitigations including upgrading to Suricata version 4.x or later, where the inspection engine has been properly fixed to terminate inspection cycles appropriately, and implementing traffic rate limiting or filtering to prevent excessive processing of suspicious content patterns. Additionally, monitoring for unusual CPU utilization patterns and implementing proper baseline performance metrics can help detect when this vulnerability is being exploited in active environments.