CVE-1999-1216 in Cisco
Summary
by MITRE
cisco routers 9.17 and earlier allow remote attackers to bypass security restrictions via certain ip source routed packets that should normally be denied using the "no ip source-route" command.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 04/03/2025
Cisco routers running software version 9.17 and earlier contain a critical security vulnerability that allows remote attackers to bypass configured security restrictions through improper handling of IP source routed packets. This vulnerability represents a fundamental flaw in the router's packet processing logic where the system fails to properly enforce the "no ip source-route" configuration directive that should prevent the acceptance of packets containing source routing information. The vulnerability exists because the router's forwarding engine does not adequately validate incoming packets against the configured source routing policies, allowing malicious actors to inject packets that contain source route options which would normally be rejected by the security configuration.
The technical implementation of this vulnerability stems from the router's failure to properly parse and validate IP header options within incoming packets. When an attacker sends an IP packet containing source route options, the router should reject such packets based on the configured security policy that disables source routing. However, due to a flaw in the packet processing code, the router accepts these packets and processes them through the normal forwarding path, effectively bypassing the intended security restriction. This behavior creates a pathway for attackers to potentially manipulate routing decisions, gain unauthorized access to network segments, or perform routing-based attacks that would normally be prevented by proper security configuration.
The operational impact of this vulnerability is significant as it undermines the fundamental security controls that network administrators rely upon to protect their infrastructure. Attackers can exploit this weakness to bypass network segmentation, potentially gaining access to restricted network zones that should be protected by the router's security policies. The vulnerability affects the integrity of the network's routing table and can be leveraged to perform various malicious activities including traffic redirection, network reconnaissance, or even more sophisticated attacks that manipulate the flow of network traffic. This weakness particularly impacts networks where source routing has been disabled as a security measure, making the system vulnerable to exploitation despite proper configuration.
Network security professionals should immediately implement mitigations including updating to Cisco IOS versions that address this vulnerability, typically versions 10.0 and later which contain the necessary patches. Organizations should also consider implementing additional network segmentation measures, monitoring for unusual source routing traffic patterns, and ensuring that proper access controls are in place to limit the potential impact of such attacks. The vulnerability aligns with CWE-1129 which describes improper handling of source routing information, and represents a clear violation of the principle of least privilege in network security. From an attacker perspective, this vulnerability maps to ATT&CK technique T1071.004 for application layer protocol: DNS and T1566.001 for credential access through network sniffing, as it provides a pathway for attackers to manipulate network traffic and potentially gain further access to sensitive resources within the network environment.