The Not-Infallible Cisco 802.1x

The 802.1x port-based security standard is often considered the
best method of security for network access control (NAC) implementations. But that’s not to say that all 802.1x implementations are always secure and bug-free.

Cisco this week reported that a pair of its 802.1x supplicants (an 802.1x component used in the client endpoints) had flaws that, if exploited, could have allowed an attacker to gain user privileges, modify files or otherwise damage the availability or confidentially of the system.

The Cisco Secure Services Client (CSSC) and a lightweight version of CSSC
included in the Cisco Trust Agent (CTA) within the Cisco Network Admission
Control (NAC) Framework had privilege escalation and password disclosure
vulnerabilities that Cisco has now corrected.

Cisco has fixed four different privilege escalation bugs. According
to Cisco’s advisory, one of the bugs could potentially have allowed an
unprivileged user who is logged into the computer to increase their
privileges to the local system user via the help facility within the
supplicant Graphical User Interface (GUI).

Another bug could have enabled a logged-in, unprivileged
user to launch any program with full system privileges.

Cisco also fixed an unintentional password disclosure bug. The advisory notes that with certain authentication methods, a user password is
logged in cleartext (i.e. non-obfuscated or encrypted) in the respective
application’s log files.

Cisco is not the only vendor that uses 802.1x as a method for deploying
NAC. StillSecure and others, such as Cisco, in the NAC space, also provide alternatives to 802.1x, including DHCP and inline approaches.

That’s not to say that the reported vulnerabilities don’t take a bit
of the shine off the 802.1x halo.

“Unfortunately, anytime vulnerabilities or security issues arise around
802.1x, its viability as the most secure method for enforcing NAC is called
into question,” Alan Shimel, chief strategy officer at access control vendor
StillSecure, told

“That being said, 802.1x remains the most secure way of testing and
controlling access to the network at the port level.”

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