Title: Cisco Access Control List Fragment Keyword Ignored Vulnerability
Severity: CRITICAL
Description:
IOS is the Cisco Internet Operating System, distributed with and used on various Cisco network hardware.
The recent addition of the 'fragment' keyword to ACL rules allows decisions based on non-initial packet fragments. This results in the rule behaving differently after checking the fragment offset in the packet, and either applying the rule or continuing to the next rule in the list.
A vulnerability in IOS on the 12000 series Cisco routers could make it possible for a remote user to send unauthorized traffic to a protected network. IOS does not filter packet fragments, even when the 'fragment' keyword is included in an ACL rule.
This vulnerability may result in attackers or users bypassing security policy.
Affected Products:
- Cisco IOS 12.0S
- Cisco IOS 12.0ST
References:
- Cisco Systems: Access Control Lists and IP Fragments
- Cisco Systems: Cisco Product Security Incident Response
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