CVE-2002-2316: Cisco Catalyst 4000 series switches running CatOS 5.5.5, 6.3.5, and 7.1.2 do not always learn MAC addresses...

Security readout for executives and security teams

This old Cisco Catalyst 4000 issue can make private one-to-one network traffic behave like broadcast traffic. If an affected switch fails to learn a MAC address from the first packet, other devices may see traffic they should not, creating a sniffing risk on legacy networks. Exposure is most likely in organizations still operating Cisco Catalyst 4000 switches with the listed CatOS versions. The practical risk depends on whether traffic is sensitive and whether an attacker can observe incorrectly broadcast traffic on the affected switching domain. Prioritize this where legacy Cisco switching still carries sensitive or regulated traffic. For modernized networks without affected hardware, urgency is low. The main business issue is unintended exposure of internal traffic, not public internet compromise. Mitigation focus: Inventory Catalyst 4000 switches and CatOS versions.; Check Cisco guidance for fixed versions or recommended replacement paths.; Retire, upgrade, or isolate affected legacy switches where possible..

Prepared

Jun 29, 2026, 02:08 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.