CVE-1999-1129: Cisco Catalyst 2900 Vlan

High severity, CVSS 7.5. EPSS: 1.6% chance of exploitation in the next 30 days.

Cisco Catalyst 2900 Virtual LAN (VLAN) switches allow remote attackers to inject 802.1q frames into another VLAN by forging the VLAN identifier in the trunking tag.

Affected products

• Cisco Catalyst 2900 Vlan: any version
• Cisco IOS: version 11.2(8)sa5 only

Published 1999-09-01. Last modified 2026-06-16.