Siemens SIMATIC CP: privilege escalation flaw under attack

What is affected

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

An improper privilege management vulnerability exists within the Siemens SIMATIC Communication Processor (CP) that allows a privileged attacker to remotely cause a denial of service.

What an attacker can do

This is a privilege escalation flaw. It lets an attacker turn limited access into full administrator control. Attackers pair it with another flaw or a malicious file: once anything of theirs runs on the device, this bug lets it take over completely.

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 Siemens SIMATIC CP 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 24, 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 3.6% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 89% of all scored vulnerabilities.

Its CVSS severity score is 7.5 out of 10 (high), as recorded in the US National Vulnerability Database.

Technical description

A vulnerability has been identified in SIMATIC CP 1543-1 (All versions < V2.0.28), SIPLUS NET CP 1543-1 (All versions < V2.0.28). Under special conditions it was possible to write SNMP variables on port 161/udp which should be read-only and should only be configured with TIA-Portal. A write to these variables could reduce the availability or cause a denial-of-service.