A high severity vulnerability described as a backdoor has been patched in several Flex System, RackSwitch and BladeCenter switches from Lenovo and IBM.
The flaw, tracked as CVE-2017-3765, affects the Enterprise Network Operating System (ENOS) running on affected devices. The vulnerability allows an attacker to gain access to the management interface of a switch.
“An authentication bypass mechanism known as ‘HP Backdoor’ was discovered during a Lenovo security audit in the Telnet and Serial Console management interfaces, as well as the SSH and Web management interfaces under certain limited and unlikely conditions,” Lenovo said in its advisory.
“This bypass mechanism can be accessed when performing local authentication under specific circumstances using credentials that are unique to each switch. If exploited, admin-level access to the switch is granted,” the company added.
ENOS is the operating system that powers Lenovo’s RackSwitch and Flex System embedded switches. ENOS was initially developed by Nortel’s Blade Server Switch Business Unit (BSSBU), which spun off in 2006 to become BLADE Network Technologies (BNT). IBM acquired BNT in 2010 and in 2014 sold it to Lenovo.
The problematic feature, introduced by Nortel in 2004 at the request of a customer, can be found in Lenovo devices and IBM Flex System, BladeCenter and RackSwitch switches that still use the ENOS firmware.
Lenovo patched the security hole with the release of ENOS 8.4.6.0 and also provided workarounds. The company says devices running the CNOS (Cloud Network Operating System) firmware are not vulnerable. IBM has also released firmware updates to fix the vulnerability in impacted switches.
Lenovo pointed out that the backdoor can only be exploited under specific circumstances.
“Lenovo is not aware of this mechanism being exploited, but we assume that its existence is known, and customers are advised to upgrade to firmware which eliminates it,” Lenovo said.
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