CVE-2007-4788 in Content Switching Modules
Summary
by MITRE
Cisco Content Switching Modules (CSM) 4.2 before 4.2.3a, and Cisco Content Switching Module with SSL (CSM-S) 2.1 before 2.1.2a, allow remote attackers to cause a denial of service (CPU consumption or reboot) via sets of out-of-order TCP packets with unspecified characteristics, aka CSCsd27478.
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Analysis
by VulDB Data Team • 07/25/2019
The vulnerability described in CVE-2007-4788 represents a critical denial of service flaw affecting Cisco Content Switching Modules and their SSL variants. This weakness specifically impacts Cisco Content Switching Modules version 4.2 prior to 4.2.3a and Cisco Content Switching Module with SSL version 2.1 prior to 2.1.2a, creating a significant operational risk for networks relying on these load balancing and content switching solutions. The vulnerability manifests when the affected systems receive carefully crafted sequences of out-of-order TCP packets that exploit implementation flaws in the TCP processing mechanisms.
The technical flaw resides in how the affected Cisco content switching modules handle TCP packet reordering during connection establishment and data transmission phases. When these systems encounter specific patterns of out-of-order TCP segments, the processing logic becomes overwhelmed, leading to excessive CPU utilization or complete system reboot conditions. This behavior stems from inadequate validation and handling of TCP sequence number mismatches that occur during normal network operations but are amplified by the specific packet characteristics that trigger the vulnerability. The unspecified characteristics of the packets suggest that the flaw may be triggered by various combinations of TCP flags, sequence numbers, and window sizes that cause the switching module to enter an infinite processing loop or memory exhaustion state.
The operational impact of this vulnerability extends beyond simple service disruption, as it can render entire content switching appliances unusable and compromise network availability. Organizations relying on these modules for load distribution, application delivery, and content switching services face potential business interruption risks when attackers exploit this weakness. The vulnerability affects critical infrastructure components that often serve as primary traffic directors for enterprise networks, making the denial of service condition particularly damaging. Additionally, the resource exhaustion characteristics can lead to cascading failures within larger network architectures where these modules serve as traffic concentrators for multiple application servers.
Mitigation strategies for this vulnerability require immediate implementation of Cisco security advisories and firmware updates to versions 4.2.3a and 2.1.2a respectively. Network administrators should also implement TCP packet filtering rules that can identify and drop suspicious out-of-order packet sequences before they reach the vulnerable systems. The implementation of rate limiting mechanisms and connection tracking improvements can help reduce the impact of potential attacks by preventing the accumulation of malformed TCP segments. Organizations should also consider network segmentation and redundant switching configurations to maintain availability during patch deployment phases. This vulnerability aligns with CWE-129, which addresses improper handling of input boundaries, and maps to ATT&CK technique T1499.004 for network denial of service attacks. The remediation process must include thorough testing of updated firmware in controlled environments before production deployment to ensure compatibility with existing network configurations and application requirements.