Cisco IOS Software: denial of service flaw under attack

What is affected

Cisco IOS Software is found on ordinary personal computers and phones, so this is not only a problem for companies. If you use it and have not updated since the fix was released, you are exposed.

A vulnerability in the Simple Network Management Protocol (SNMP) subsystem of Cisco IOS Software running on certain models of Cisco Catalyst Switches could allow an authenticated, remote attacker to cause 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

A basic user account

Does the victim have to do something?

No, works without the victim doing anything

What to do

1. Update Cisco IOS Software now. Open the update or "About" screen, install whatever is offered and restart the app or device, because the fix is not active until you do.
2. Turn on automatic updates so the next fix arrives without you having to look for it.
3. If your device is too old to receive this update, stop using the affected app for anything sensitive and plan a replacement.

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 4.1% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 91% of all scored vulnerabilities.

Its CVSS severity score is 6.3 out of 10 (medium), as recorded in the US National Vulnerability Database.

Technical description

A vulnerability in the Simple Network Management Protocol (SNMP) subsystem of Cisco IOS Software running on certain models of Cisco Catalyst Switches could allow an authenticated, remote attacker to cause a denial of service (DoS) condition, aka a GET MIB Object ID Denial of Service Vulnerability. The vulnerability is due to a condition that could occur when the affected software processes an SNMP read request that contains a request for the ciscoFlashMIB object ID (OID). An attacker could trigger this vulnerability by issuing an SNMP GET request for the ciscoFlashMIB OID on an affected device. A successful exploit could cause the affected device to restart due to a SYS-3-CPUHOG. This vulnerability affects the following Cisco devices if they are running a vulnerable release of Cisco IOS Software and are configured to use SNMP Version 2 (SNMPv2) or SNMP Version 3 (SNMPv3): Cisco Catalyst 2960-L Series Switches, Cisco Catalyst Digital Building Series Switches 8P, Cisco Catalyst Digital Building Series Switches 8U. Cisco Bug IDs: CSCvd89541.