CVE-2026-21588 Denial of service in Confluence Data Center
An authenticated attacker can cause a denial of service in Confluence Data Center, disrupting availability for intended users.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-21588?
CVE-2026-21588 is a high-severity denial of service vulnerability in Atlassian Confluence Data Center, published on 15 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
This High severity DoS (Denial of Service) vulnerability was introduced in versions 8.9.0, 9.0.1, 9.1.0, 9.2.0, 9.3.1, 9.4.0, 9.5.1, 10.0.2, 10.1.0, and 10.2.0 of Confluence Data Center. This DoS (Denial of Service) vulnerability, with a CVSS Score of 7.1, allows an authenticated attacker to cause a resource to be unavailable for its intended users by temporarily or indefinitely disrupting services of a host connected to a network. Atlassian recommends that Confluence Data Center customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions: Confluence Data Center 9.2: Upgrade to a release greater than or equal to 9.2.24 Confluence Data Center 10.2: Upgrade to a release greater than or equal to 10.2.17 See the release notes ([https://confluence.atlassian.com/doc/confluence-release-notes-327.html]). You can download the latest version of Confluence Data Center from the download center ([https://www.atlassian.com/software/confluence/download-archives]). This vulnerability was reported via our Penetration Testing program.
Weakness: CWE-400
Which versions are affected by CVE-2026-21588?
How do I fix CVE-2026-21588?
No fix has been published for CVE-2026-21588 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-21588 being exploited?
There is no known exploitation of CVE-2026-21588 in the wild and no public exploit code.
Sources
Also known as GHSA-4848-75hf-436m.