CVE-2023-22527

Atlassian Confluence Data Center and Server contain an unauthenticated OGNL template injection vulnerability (CWE-74) in which attacker-controlled input is evaluated by the application as an OGNL expression. A remote, unauthenticated attacker can trigger the flaw by sending a crafted HTTP request that injects OGNL expressions, which the server then executes. Successful exploitation leads to remote code execution on the host running Confluence, giving the attacker control of the system without any credentials. Any organization running self-hosted Confluence Data Center or Server is potentially affected — the available data does not specify version ranges, so operators should consult Atlassian's advisory — with internet-facing instances at highest risk. Exploitation is active: the flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2024-01-24 with known ransomware use, and EPSS assigns it a 100% probability of exploitation within 30 days (100th percentile).

What to do: Patch to the fixed release specified in Atlassian's advisory immediately, prioritizing internet-exposed instances, since the flaw is in CISA's KEV with known ransomware use and carries a 100% EPSS. If patching is not immediately possible, apply the vendor's mitigations per the KEV required action — or discontinue/restrict use — for example by limiting unauthenticated access to Confluence from the internet. Review Confluence access and application logs for anomalous unauthenticated requests and indicators of command execution or ransomware activity.