Security alert for GPRS networks based on Nokia GGSN
Posted on 14-Jun-2003 11:42
Filed under: News
A security flaw has been reported in the Nokia GGSN (Gateway GPRS support node) that could have lead to a Denial of Service (DoS) attack by hackers. The GGSN is the platform that exists between Gn and Gi networks within a GPRS network. @stake notified Nokia of the vulnerability, and Nokia has issued a software update to close the loophole. @stake says that there exists a vulnerability in the TCP stack that allows an attacker to cause the GGSN to kernel panic and shutdown. This potentially allows an attacker to crash all data connectivity within a GPRS based network. This vulnerability is exploited by sending a malformed IP packet with a TCP option of 0xFF over a cellphone to the affected network.
In a statement sent to all of Nokia GGSN customers, the company said "Under exceptional circumstances Nokia GGSN release 1 is potentially vulnerable to a "Denial Of Service" style of attack from a malicious user equipped with a computer and a mobile phone. When the vulnerability is exploited the GGSN restarts. There is no damage to the configuration, but some charging data may be lost. Changing a normal Access Point to tunneled (GRE or IP in IP) prevents the attacks from mobile user side.
As an interim measure operators can perform the following preventative configuration changes to their networks. Ensure that all IP packets with non standard IP options are dropped by boarder firewalls on the Gi interface. Within the Gn network ensure that the GTP aware firewall (if present) also drops all encapsulated IP packets with non standard IP options. This may introduce latency however it will mitigate against the attack until the patch has been fully deployed and tested.