CVE-2017-6658 in Snort++
Summary
by MITRE
Cisco Sourcefire Snort 3.0 before build 233 has a Buffer Overread related to use of a decoder array. The size was off by one making it possible to read past the end of the array with an ether type of 0xFFFF. Increasing the array size solves this problem.
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Analysis
by VulDB Data Team • 09/28/2020
The vulnerability identified as CVE-2017-6658 affects Cisco Sourcefire Snort 3.0 versions prior to build 233, representing a critical buffer overread condition that stems from improper array boundary handling within the software's packet decoding mechanisms. This flaw exists within the decoder array implementation where the allocated memory size is incorrectly calculated by exactly one element, creating a scenario where maliciously crafted network packets can trigger memory access violations. The specific trigger condition involves packets with an ether type field set to 0xFFFF, which is a valid but uncommon ethernet frame type that can be exploited to cause the software to access memory beyond the intended array boundaries. The vulnerability falls under the CWE-121 category of Buffer Overflow, specifically manifesting as a heap-based buffer overread that can lead to unpredictable behavior and potential system compromise.
The technical exploitation of this vulnerability requires an attacker to craft network packets with the specific ether type value of 0xFFFF, which when processed by the affected Snort version causes the decoder array to attempt accessing memory locations beyond its allocated bounds. This overread condition occurs because the software's memory management logic fails to account for the exact array size requirement, resulting in a single-byte buffer overrun that can expose sensitive data or cause application instability. The impact is particularly concerning in network monitoring and intrusion detection contexts where Snort operates as a critical security tool, as this vulnerability could be leveraged to extract information from memory or potentially cause denial of service conditions that would compromise network security monitoring capabilities.
The operational implications of CVE-2017-6658 extend beyond simple memory corruption, as it represents a fundamental flaw in the software's defensive programming practices and memory boundary validation mechanisms. Network security administrators must recognize that this vulnerability could be exploited in the context of the ATT&CK framework's reconnaissance and resource development phases, where attackers might use such flaws to gather intelligence about network infrastructure or establish persistent access points. The vulnerability's exploitation could lead to information disclosure, system instability, or potentially provide a foothold for more sophisticated attacks within network environments where Snort is deployed as a primary security monitoring solution. Organizations running affected versions should prioritize immediate patching to prevent potential exploitation in their security monitoring infrastructure.
Mitigation strategies for this vulnerability center on applying the official Cisco patch that increases the array size to properly accommodate all valid ether type values, including the problematic 0xFFFF value. The fix addresses the root cause by ensuring that the decoder array allocation matches the actual range of possible input values, thereby preventing the buffer overread condition from occurring. Security teams should also implement network segmentation and monitoring to detect anomalous packet patterns that might indicate attempted exploitation of this vulnerability, while maintaining awareness of the specific ATT&CK techniques that could leverage such buffer overread conditions for information gathering or system compromise. Regular vulnerability assessments and patch management procedures should be reinforced to prevent similar issues in other network security tools and applications that might exhibit similar memory boundary handling flaws.