Sysadmins can look forward to clocking some overtime this week after Cisco warned of flaws in how its core operating system handles malformed Secure Sockets Layer (SSL) traffic.

Several types of SSL messages (such as ClientHello and ChangeCipherSpec), when malformed, can crash vulnerable appliances running IOS, which are configured to accept SSL protocol packets. The scope of the vulnerability is confined to denial of service attacks. There's no code execution or snooping risk.

Exploitation would involving sending malformed packets during the SSL protocol exchange with the vulnerable devices, such as SSL VPNs or routers, to potentially carry out a sustained denial of service attack.

Although the vulnerability could be more severe, a wide range of devices are affected. All of which adds up to plenty of work for the BOFHs of this world in applying software updates or workarounds as explained in a Cisco advisory here.

In other network security news, flaws in how content scanning systems parse Unicode encoded traffic have been unearthed. The shortcomings, which potentially affect a wide range of products from multiple vendors, create a means to slip malicious HTTP traffic past content scanning systems such as intrusion prevention systems.

Kit from 3Com, Cisco and EMC are known to be vulnerable while a large number of other vendors of high-tech burglar alarms are assessing the scope of the problem. Users of Snort, the popular open-source intrusion detection software package, are known to be in the clear. ®