Fortra Cobalt Strike: code execution flaw under attack

What is affected

Fortra Cobalt Strike 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.

Fortra Cobalt Strike User Interface contains an unspecified vulnerability rooted in Java Swing that may allow remote code execution.

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 Fortra Cobalt Strike 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.

Vendor advisories and fixes

• cobaltstrike.comwww.cobaltstrike.com/blog/out-of-band-update-cobalt-strike-4-7-2/

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on March 30, 2023, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by April 20, 2023, 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 2.7% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 86% 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

Cobalt Strike 4.7.1 fails to properly escape HTML tags when they are displayed on Swing components. By injecting crafted HTML code, it is possible to remotely execute code in the Cobalt Strike UI.