Cisco VPN Routers: code execution flaw under attack

What is affected

Cisco VPN Routers are mostly run by companies, schools and public bodies, not on home computers. You are unlikely to have them yourself, but organisations that hold your data may. Breaches that start with flaws like this one are how personal data ends up leaked.

A vulnerability in the web interface of the Cisco VPN Routers could allow an unauthenticated, remote attacker to execute arbitrary code as root and gain full control of an affected system.

What an attacker can do

This is a code execution flaw. It lets an attacker run their own commands or programs on the affected system. In practice that usually means taking it over: installing malware, stealing data or using it to reach other devices on the same network.

How it is reached

Over the internet or network

Access the attacker needs

No account needed

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. At home: nothing to install. Keep your own devices updated and use a different password for every service, so that a breach at one organisation does not open your other accounts.
2. If you administer Cisco VPN Routers at work: apply the vendor's fix or mitigation now and review logs for signs of compromise, because the flaw was being exploited before it was listed.
3. If the product is past its support date and no fix exists, take it off the internet or retire it.

Apply updates per vendor instructions.

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on March 25, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by April 15, 2022, a deadline that has already passed. That deadline does not bind anyone else, but it shows how seriously the agency rates it.

The EPSS model estimates a 55% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 99.0% of all scored vulnerabilities.

Its CVSS severity score is 9.8 out of 10 (critical), as recorded in the US National Vulnerability Database.

Technical description

A vulnerability in the web interface of the Cisco RV132W ADSL2+ Wireless-N VPN and RV134W VDSL2 Wireless-AC VPN Routers could allow an unauthenticated, remote attacker to execute arbitrary code and gain full control of an affected system, including issuing commands with root privileges. The attacker could also cause an affected system to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to an incomplete input validation on user-controlled input in an HTTP request to the targeted device. An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected system. A successful exploit could allow the attacker to execute arbitrary code as the root user and gain full control of the affected system or cause it to reload, resulting in a DoS condition. This vulnerability is fixed in firmware version 1.0.1.11 for the following Cisco products: RV132W ADSL2+ Wireless-N VPN Router and RV134W VDSL2 Wireless-AC VPN Router. Cisco Bug IDs: CSCvg92737, CSCvh60170.