Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches: denial of service flaw under attack

What is affected

Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches 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 Bidirectional Forwarding Detection (BFD) offload implementation of Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches could allow an unauthenticated, remote attacker to cause a crash of the iosd process, causing a denial-of-service (DoS) condition.

What an attacker can do

This is a denial of service flaw. It lets an attacker crash the product or make it unavailable to the people who rely on it.

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 Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches 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 3, 2022, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by March 17, 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 7.7% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 94% of all scored vulnerabilities.

Its CVSS severity score is 8.6 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

A vulnerability in the Bidirectional Forwarding Detection (BFD) offload implementation of Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches could allow an unauthenticated, remote attacker to cause a crash of the iosd process, causing a denial of service (DoS) condition. The vulnerability is due to insufficient error handling when the BFD header in a BFD packet is incomplete. An attacker could exploit this vulnerability by sending a crafted BFD message to or across an affected switch. A successful exploit could allow the attacker to trigger a reload of the system. This vulnerability affects Catalyst 4500 Supervisor Engine 6-E (K5), Catalyst 4500 Supervisor Engine 6L-E (K10), Catalyst 4500 Supervisor Engine 7-E (K10), Catalyst 4500 Supervisor Engine 7L-E (K10), Catalyst 4500E Supervisor Engine 8-E (K10), Catalyst 4500E Supervisor Engine 8L-E (K10), Catalyst 4500E Supervisor Engine 9-E (K10), Catalyst 4500-X Series Switches (K10), Catalyst 4900M Switch (K5), Catalyst 4948E Ethernet Switch (K5). Cisco Bug IDs: CSCvc40729.