Cisco Patches IOS Security Flaws

The most serious vulnerability could allow malicious hackers to access network resources.

Routing and switching giant Cisco Systems has released patches for a pair of denial-of-service and system-access flaws affecting a range of IOS-based devices.

The most serious of the two flaws was discovered in the way the Cisco IOS (Internetwork Operating System) processes certain IKE (Internet Key Exchange) Xauth messages when configured to be an Easy VPN Server.

"Successful exploitation of these vulnerabilities may permit an unauthorized user to complete authentication and potentially access network resources," San Jose, Calif.-based Cisco Systems Inc. said in an advisory.

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The IKE issue affects all Cisco devices running any unfixed version of Cisco IOS that supports, and is configured for, Cisco Easy VPN Server Xauth Version 6 authentication.

Click here to read about Ciscos plans to target mesh networking.

The company warned that certain packets sent to the IOS Easy VPN Server listening on UDP (User Datgram Protocol) port 500 may permit an unauthorized user to complete Xauth authentication and thereby gain access to network resources.

In order for the attack to succeed, an attacker must know the shared group key to complete the IKE Phase 1 negotiation before the Xauth negotiation takes place, Cisco explained.

Cisco also rolled out free patches to cover the vulnerability.

A separate advisory with patches also was issued to correct a denial-of-service flaw affecting Cisco IOS devices that support, and are configured to use, the SSH (Secure Shell) server functionality.

Cisco IOS supports both versions of the SSH (SSH v1 and SSH v2), the protocol that provides security and remote connection to a network device.

When acting as an SSH v2 server for remote management and authenticating against a TACACS+ server, the company said unpatched devices will return an error when authenticating against a TACACS+ server. That can be exploited to cause a vulnerable device to reload.

The company also fixed a memory leak that occurs when authenticating SSH users against a TACACS+ server and login fails due to invalid credentials. This can be exploited by malicious hackers to exhaust memory resources.

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