Atlassian Confluence Data Center and Server: code execution flaw under attack

What is affected

Atlassian Confluence Data Center and Server 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.

Atlassian Confluence Data Center and Server contain an unauthenticated OGNL template injection vulnerability that can lead to 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

CISA records this vulnerability as known to be used in ransomware campaigns: attackers use it to get in, then encrypt files and demand payment.

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 Atlassian Confluence Data Center and Server 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 mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Vendor advisories and fixes

• confluence.atlassian.comconfluence.atlassian.com/security/cve-2023-22527-rce-remote-code-execution-vulnerability-i

How urgent is it

CISA added this vulnerability to its Known Exploited Vulnerabilities catalogue on January 24, 2024, which means there is reliable evidence of attacks in the wild. US federal agencies must fix it by February 14, 2024, 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 100% probability that this flaw will be exploited somewhere in the next 30 days. That is higher than 100.0% 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

A template injection vulnerability on older versions of Confluence Data Center and Server allows an unauthenticated attacker to achieve RCE on an affected instance. Customers using an affected version must take immediate action. Most recent supported versions of Confluence Data Center and Server are not affected by this vulnerability as it was ultimately mitigated during regular version updates. However, Atlassian recommends that customers take care to install the latest version to protect their instances from non-critical vulnerabilities outlined in Atlassian’s January Security Bulletin.