Disable TELNET! Cisco finds 0-Day in CIA Dump affecting over 300 Network Switch Models
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2017-3881 | Unauthenticated RCE in Cisco IOS/IOS XE switches via malformed CMP Telnet options CVE-2017-3881 is a critical (CVSS 9.8) unauthenticated remote code execution flaw, classified CWE-20, in the Cluster Management Protocol (CMP) processing code of Cisco IOS and IOS XE, which uses Telnet internally for signaling between switch cluster members. Because affected devices accept CMP-specific Telnet options on any inbound Telnet connection and mishandle malformed ones, an unauthenticated attacker who opens a Telnet session to a Telnet-enabled device and sends malformed CMP options can trigger the flaw. Successful exploitation lets the attacker execute arbitrary code with elevated privileges, gaining full control of the device, or force a reload of the switch. Affected hardware spans over 300 switching models per related coverage — Catalyst switches, Embedded Service 2020 and IE Industrial Ethernet switches, several EtherSwitch service modules, the ME 4924-10GE, RF Gateway 10, and the CGESM module for HP — running IOS or IOS XE with Telnet enabled; devices that accept only SSH are not remotely exploitable. The bug was disclosed via the March 2017 WikiLeaks Vault 7 CIA leak (tied to the 'Zero Disco' toolkit in related coverage), patched by Cisco that month, has a public PoC (Exploit-DB 41872), was added to CISA's KEV on 2022-03-25 (ransomware use unknown), and EPSS rates a 99% probability of exploitation in 30 days (100th percentile), so in-the-wild exploitation should be assumed. Do: Upgrade affected switches to the fixed IOS/IOS XE releases listed in Cisco's advisory for bug CSCvd48893 (the CISA KEV required action is to apply the vendor updates). Until patched, disable Telnet on vty lines and use SSH, or restrict inbound TCP/23 to trusted management hosts, since the bug is only reachable via inbound Telnet sessions. Audit configurations for 'transport input telnet' and prioritize internet-facing or widely reachable Catalyst, IE industrial, and EtherSwitch-service-module devices. | 9.8 | 99% | KEV PoC |
| mass≈1M+ deployed affected switches across 300+ models (only the Telnet-enabled subset is exploitable, likely hundreds of thousands of exposed systems) |
Full article494 words · extracted from thehackernews.com · click to collapse
Swati KhandelwalMar 20, 2017
Cisco is warning of a new critical zero-day IOS / IOS XE vulnerability that affects more than 300 of its switch models.
The company identified this highest level of vulnerability in its product while analyzing "Vault 7" — a roughly 8,761 documents and files leaked by Wikileaks last week, claiming to detail hacking tools and tactics of the Central Intelligence Agency (CIA).
The vulnerability resides in the Cluster Management Protocol (CMP) processing code in Cisco IOS and Cisco IOS XE Software.
If exploited, the flaw (CVE-2017-3881) could allow an unauthenticated, remote attacker to cause a reboot of an affected device or remotely execute malicious code on the device with elevated privileges to take full control of the device, Cisco says in its advisory.
The CMP protocol has been designed to pass around information about switch clusters between cluster members using Telnet or SSH.
The vulnerability is in the default configuration of affected Cisco devices, even if the user doesn't configure any cluster configuration commands. The flaw can be exploited during Telnet session negotiation over either IPv4 or IPv6.
According to the Cisco researchers, this bug occurs in Telnet connections within the CMP, due to two factors:
- The protocol doesn't restrict the use of CMP-specific Telnet options only to internal, local communications between cluster members; instead, it accepts and processes commands over any Telnet connection to an affected device.
- The incorrect processing of malformed CMP-specific Telnet options.
So, in order to exploit this vulnerability, an attacker can send "malformed CMP-specific Telnet options while establishing a Telnet session with an affected Cisco device configured to accept Telnet connections," researchers say.
This exploitation could allow the attacker to remotely execute malicious code and obtain full control of the affected device or cause a reload of the affected device.
Disable Telnet On Vulnerable Models — Patch is not Available Yet!
The vulnerability affects 264 Catalyst switches, 51 industrial Ethernet switches, and 3 other devices, which includes Catalyst switches, Embedded Service 2020 switches, Enhanced Layer 2/3 EtherSwitch Service Module, Enhanced Layer 2 EtherSwitch Service Module, ME 4924-10GE switch, IE Industrial Ethernet switches, RF Gateway 10, SM-X Layer 2/3 EtherSwitch Service Module, and Gigabit Ethernet Switch Module (CGESM) for HP. (check complete list here)
Currently, this vulnerability is unpatched, and until patches are available, Cisco recommends its users to disable the Telnet connection to the switch devices in favor of SSH.
The company's advisory doesn't talk about any working exploit using this flaw, but if there's one, tens of thousands, if not hundreds of thousands, of devices installed around the world look to have been at great risk for an unknown period — Thanks to the CIA for holding the flaw.
Cisco will update its IOS Software Checker tool immediately as soon as the patches come out.
Found this article interesting? Follow us on Google News, Twitter and LinkedIn to read more exclusive content we post.
Text extracted automatically; images, tables and formatting may be missing. Original: https://thehackernews.com/2017/03/cisco-network-switch-exploit.html