CVE-2026-21579 is an information disclosure vulnerability in Atlassian Confluence Data Center with a CVSS 4.0 base score of 8.2 (high severity). It affects specific versions including 7.17.0, 7.19.0, 8.5.0, 8.9.0, 9.0.1, 9.1.0, 9.2.0, 10.0.2, 10.1.0, and 10.2.0. The vulnerability enables unauthenticated attackers to view sensitive information. Atlassian advises upgrading to versions >=9.2.22 or >=10.2.14 depending on the branch to mitigate the risk. No known exploits in the wild have been reported at this time.

An unauthenticated attacker can exploit this vulnerability to disclose sensitive information from affected Confluence Data Center instances. This could lead to exposure of confidential data, potentially aiding further attacks or information leakage. The vulnerability does not require authentication and has a high severity rating, indicating significant risk if left unpatched.

Atlassian recommends upgrading affected Confluence Data Center instances to fixed versions: 9.2.22 or later for the 9.2.x branch, and 10.2.14 or later for the 10.2.x branch. Users unable to upgrade to the latest version should at minimum apply these updates. Patch status is confirmed by the vendor's advisory. No alternative mitigations or temporary fixes are indicated.