Cisco warns WLAN controller, 9000 series router and IOS/XE users to patch urgent security holes

Cisco says unpatched vulnerabilities could lead to DoS attacks, arbitrary code execution, take-over of devices.

Cisco this week issued 31 security advisories but directed customer attention to “critical” patches for its IOS and IOS XE Software Cluster Management and IOS software for Cisco ASR 9000 Series routers. A number of other vulnerabilities also need attention if customers are running Cisco Wireless LAN Controllers.

The first critical patch has to do with a vulnerability in the Cisco Cluster Management Protocol (CMP) processing code in Cisco IOS and Cisco IOS XE Software that could allow an unauthenticated, remote attacker to send malformed CMP-specific Telnet options while establishing a Telnet session with an affected Cisco device configured to accept Telnet connections. An exploit could allow an attacker to execute arbitrary code and obtain full control of the device or cause a reload of the affected device, Cisco said.

The problem has a Common Vulnerability Scoring System number of 9.8 out of 10.

According to Cisco, the Cluster Management Protocol utilizes Telnet internally as a signaling and command protocol between cluster members. The vulnerability is due to the combination of two factors:

  • The failure to restrict the use of CMP-specific Telnet options only to internal, local communications between cluster members and instead accept and process such options over any Telnet connection to an affected device
  • The incorrect processing of malformed CMP-specific Telnet options.

Cisco says the vulnerability can be exploited during Telnet session negotiation over either IPv4 or IPv6. This vulnerability can only be exploited through a Telnet session established to the device; sending the malformed options on Telnet sessions through the device will not trigger the vulnerability.

The company says there are no workarounds for this problem, but disabling Telnet as an allowed protocol for incoming connections would eliminate the exploit vector. Cisco recommends disabling Telnet and using SSH instead. Information on how to do both can be found on the Cisco Guide to Harden Cisco IOS Devices. For patch information go here.

The second critical patch involves a vulnerability in the sysadmin virtual machine (VM) on Cisco’s ASR 9000 carrier class routers running Cisco IOS XR 64-bit Software could let an unauthenticated, remote attacker access internal applications running on the sysadmin VM, Cisco said in the advisory.  This CVSS also has a 9.8 rating.

Cisco said the vulnerability is due to incorrect isolation of the secondary management interface from internal sysadmin applications. An attacker could exploit this vulnerability by connecting to one of the listening internal applications. A successful exploit could result in unstable conditions, including both denial of service (DoS) and remote unauthenticated access to the device, Cisco stated.

Cisco has released free software updates that address the vulnerability described in this advisory.

Lastly, Cisco wrote that multiple vulnerabilities in the administrative GUI configuration feature of Cisco Wireless LAN Controller (WLC) Software could let an authenticated, remote attacker cause the device to reload unexpectedly during device configuration when the administrator is using this GUI, causing a DoS condition on an affected device. The attacker would need to have valid administrator credentials on the device for this exploit to work, Cisco stated.

“These vulnerabilities are due to incomplete input validation for unexpected configuration options that the attacker could submit while accessing the GUI configuration menus.

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