CVE-2003-0567: Cisco IOS 11.x and 12.0 through 12.2 allows remote attackers to cause a denial of service (traffic block) b...

Security readout for executives and security teams

This CVE affects legacy Cisco IOS software and can let a remote attacker block traffic through a device interface using a specific IPv4 packet sequence. For an executive, the main risk is network availability: an exposed affected device could stop forwarding traffic on the targeted interface. Exposure is most likely in organizations still operating Cisco IOS 11.x or 12.0 through 12.2 on devices with IPv4 interfaces reachable by untrusted traffic. Modern, upgraded, or decommissioned IOS deployments may not be exposed, but this must be verified from asset inventory. Treat this as a legacy infrastructure availability risk. It is old, but affected internet-facing or partner-facing network devices could create business disruption. Prioritize verification and vendor-guided remediation over emergency response unless exposure or symptoms are found. Mitigation focus: Inventory Cisco IOS versions across network infrastructure.; Prioritize devices running IOS 11.x or 12.0 through 12.2.; Review the Cisco advisory for fixed releases or documented workarounds..

Prepared

Jun 30, 2026, 09:31 UTC (UTC+00:00)

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