CVE-2017-3885 in Firepower System Software
Summary
by MITRE
A vulnerability in the detection engine reassembly of Secure Sockets Layer (SSL) packets for Cisco Firepower System Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition because the Snort process consumes a high level of CPU resources. Affected Products: This vulnerability affects Cisco Firepower System Software running software releases 6.0.0, 6.1.0, 6.2.0, or 6.2.1 when the device is configured with an SSL policy that has at least one rule specifying traffic decryption. More Information: CSCvc58563. Known Affected Releases: 6.0.0 6.1.0 6.2.0 6.2.1.
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2017-3885 resides within the SSL packet detection engine reassembly functionality of Cisco Firepower System Software, representing a critical security flaw that can be exploited remotely without authentication. This issue specifically targets devices operating on software releases 6.0.0, 6.1.0, 6.2.0, and 6.2.1 when configured with SSL policies containing at least one rule that specifies traffic decryption. The vulnerability stems from improper handling of SSL packet reassembly processes within the Snort detection engine, creating a condition where maliciously crafted SSL traffic can trigger excessive CPU resource consumption.
The technical flaw manifests when the Snort process encounters specially crafted SSL packets that exploit weaknesses in the reassembly logic of the SSL detection engine. This weakness allows an attacker to craft packets that cause the system to enter an infinite loop or consume disproportionate CPU cycles during the SSL packet reassembly phase. The vulnerability is particularly dangerous because it operates at the core detection engine level where all SSL traffic must pass through for inspection, making it a fundamental component of the device's security posture. The flaw can be categorized under CWE-400 as an Uncontrolled Resource Consumption vulnerability, specifically manifesting as a denial of service condition.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire network security infrastructure. When exploited, the vulnerability causes the Snort process to consume excessive CPU resources, leading to significant performance degradation that can render the firewall ineffective in protecting network traffic. This DoS condition can persist for extended periods, potentially causing complete service unavailability while the device struggles to process the malicious traffic patterns. Network administrators may experience complete loss of visibility into SSL traffic, effectively creating a security blind spot that leaves the network vulnerable to other attacks. The vulnerability's exploitation can occur without any authentication requirements, making it particularly dangerous as attackers can target the system from external networks.
Mitigation strategies for CVE-2017-3885 should focus on immediate software updates to patched versions of Cisco Firepower System Software, as well as implementing temporary network segmentation and traffic filtering measures. Organizations should prioritize applying the relevant security patches provided by Cisco to address the root cause of the vulnerability. Network administrators should also consider implementing rate limiting and traffic shaping policies that can help prevent the exploitation of this vulnerability by limiting the volume of SSL traffic that can be processed simultaneously. Additionally, monitoring for unusual CPU utilization patterns and implementing intrusion detection rules specific to this vulnerability can help detect exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1499.004 for Network Denial of Service, highlighting the need for both preventive and detective controls to protect against such attacks. Organizations should also consider implementing redundant security controls to ensure that a single point of failure does not compromise overall network security posture.