Executive brief
A security flaw in Cisco IOS software could allow unauthorized network traffic to bypass intended security filters. This affects routers and switches using specific TACACS configurations, potentially allowing attackers to access restricted parts of the corporate network. Such a breach could lead to unauthorized data access or disruption of internal services.
Technical details
A vulnerability exists in Cisco IOS 10.3 within the processing of extended IP Access Control Lists (ACLs). When an ACL is configured using the 'tacacs' or 'tacacs-ds' keywords, the filtering logic may be bypassed, allowing traffic that should be denied to pass through the interface. This is a network-based attack that requires no authentication. An attacker can exploit this to reach protected network segments or bypass security boundaries established by the router. Users should upgrade to a patched version of IOS or remove the affected keywords from their ACL configurations.
Affected products
- Cisco IOS 10.3
Timeline
- 1995-07-31: disclosed