CVE-2017-12300 in Firepower System Software
Summary
by MITRE
A vulnerability in the SNORT detection engine of Cisco Firepower System Software could allow an unauthenticated, remote attacker to bypass a file policy that is configured to block the Server Message Block Version 2 (SMB2) protocol. The vulnerability is due to the incorrect detection of an SMB2 file when the detection is based on the length of the file. An attacker could exploit this vulnerability by sending a crafted SMB2 transfer request through the targeted device. A successful exploit could allow the attacker to bypass filters that are configured to block SMB2 traffic. Cisco Bug IDs: CSCve58398.
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2017-12300 resides within the snort detection engine component of Cisco Firepower System Software, representing a critical security flaw that undermines network traffic filtering capabilities. This weakness specifically targets the Server Message Block Version 2 protocol implementation and manifests as an improper handling of file detection logic based on file length attributes. The vulnerability architecture stems from the software's inability to accurately identify SMB2 traffic patterns when file size metrics are used as primary detection parameters, creating a pathway for malicious actors to circumvent security controls that should prevent SMB2 protocol access.
The technical exploitation mechanism leverages a fundamental flaw in the snort engine's packet analysis algorithms where SMB2 protocol detection fails when file length characteristics do not match expected patterns. Attackers can craft specific SMB2 transfer requests that manipulate file size parameters to evade the detection system, effectively bypassing configured file policies designed to block SMB2 traffic. This misclassification occurs because the detection engine relies on incomplete heuristic analysis that fails to account for legitimate SMB2 file transfer variations that might occur with differently sized files. The vulnerability's exploitation requires only remote access without authentication credentials, making it particularly dangerous as it can be executed from external network positions without requiring insider access or elevated privileges.
The operational impact of this vulnerability extends beyond simple protocol bypass, as it compromises the fundamental integrity of network security policies implemented through Cisco Firepower systems. Organizations relying on these devices for SMB2 traffic blocking may experience unauthorized access to network resources, potentially leading to data exfiltration, lateral movement, or other malicious activities. The flaw affects the core filtering capabilities of the system, meaning that any security policies configured to restrict SMB2 access become ineffective against this specific attack vector. Network defenders face the challenge of maintaining visibility into SMB2 traffic that should be blocked while simultaneously dealing with the increased risk of unauthorized access to sensitive network resources.
Mitigation strategies for CVE-2017-12300 should prioritize immediate software updates from Cisco addressing the snort engine detection logic flaws. Organizations must implement network segmentation to isolate critical systems from potential SMB2 traffic, while also deploying additional monitoring solutions to detect anomalous SMB2 behavior patterns. The vulnerability aligns with attack techniques documented in the MITRE ATT&CK framework under the T1071.004 sub-technique for application layer protocol manipulation, and represents a specific implementation weakness that could be categorized under CWE-20 as improper input validation. Security teams should conduct comprehensive network traffic analysis to identify potential exploitation attempts and establish baseline SMB2 traffic patterns for anomaly detection. Regular security assessments of network filtering systems are essential to prevent similar detection engine flaws from compromising network security posture and maintaining the integrity of access control policies.