Cisco RV Series Routers: code execution flaw under attack

What is affected

Cisco RV Series 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 deserialization of untrusted data vulnerability in the web-based management interface of certain Cisco Small Business RV Series Routers could allow an attacker to execute code with root privileges.

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

A basic user account

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 RV Series 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 June 8, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by June 22, 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 5.5% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 93% of all scored vulnerabilities.

Its CVSS severity score is 8.8 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

A vulnerability in the web-based management interface of certain Cisco Small Business RV Series Routers could allow an authenticated, remote attacker to execute arbitrary commands with root privileges. The attacker must have either a valid credential or an active session token. The vulnerability is due to lack of input validation of the HTTP payload. An attacker could exploit this vulnerability by sending a malicious HTTP request to the web-based management interface of the targeted device. A successful exploit could allow the attacker to execute commands with root privileges.