Cisco warns of critical IOS flaws

Attackers could exploit multiple flaws in Cisco's IOS to cause a denial of service or remotely execute arbitrary code.

Cisco is warning customers about multiple vulnerabilities in its Cisco Internework Operating System (IOS) and IOS secure copy server as well as its Unified Communications Manager, which could be exploited remotely by an attacker to conduct a denial of service or execute arbitrary code.

Cisco said multiple vulnerabilities occur in its IOS and Unified Communications Manager when handling malformed Session Initiation Protocol (SIP) packets. SIP is a standard protocol for initiating an interactive user session that involves multimedia elements such as video, voice, chat, gaming, and virtual reality.

Cisco said the router can be crashed by a malformed SIP message. A memory leak and memory corruption also can occur when processing a malformed SIP message, Cisco said in its advisory. Cisco IOS versions 12.0 through 12.4 are vulnerable and Cisco Unified Communications Manager versions 5.1 through 6.0 are vulnerable. Patches are being released.

In addition the IOS is prone to a remote buffer-overflow vulnerability because it fails to perform adequate boundary checks on user supplied data. Also, Cisco said its IOS secure copy server is prone to a remote security-bypass vulnerability.

Danish vulnerability clearinghouse Secunia rated the flaws "moderately critical." Symantec's DeepSight Threat Management System said Cisco customers can block external access at the network boundary, unless external parties require service until the software is updated.

"If global access isn't needed, filter access to the affected device at the network boundary," Symantec said in its advisory. "Restricting access to only trusted computers and networks might greatly reduce the likelihood of exploitation."

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