The networking giant said the flaws, in the Optical Networking System 15000 series, could be exploited by malicious users for a denial of service (DoS) attack or to compromise a system.
The first four flaws are for the Cisco ONS 15310-CL and 15327 series, the 15454 MSTP and MSPP series and the 15600 series.
One flaw leaves multiple services vulnerable to acknowledgement code (ACK) DoS attacks where an invalid response is sent to the user during a three-way handshake, according to vulnerability monitoring firm Secunia.
The set also includes two flaws where the error "within the processing of IP packets can be exploited to reset the control cards by sending a specially crafted IP packet," according to Secunia, and an exploitable error within the processing of "Open Shortest Path First" packets.
The first four new vulnerabilities can be fixed by downloading updated software versions from Cisco.
The fifth newly disclosed vulnerability exists within the Cisco Transport Controller applet launcher, downloaded each time a management connection is made to the optical node, according to Secunia.
The flaw can be fixed by updating to the Cisco Transport Controller version 4.1.0 or later.
Cisco also recommended that users disable HTTP compression as a workaround.