What is CVE-2026-21584?

CVE-2026-21584 is a high-severity vulnerability in Atlassian Bamboo, classified under Improper Authorization. CVSS score: 8.1/10. Published 2026-08-18.

How severe is CVE-2026-21584?

High severity. CVSS v3 base score is 8.1 out of 10.

Auth bypass in Atlassian Bamboo

CVE-2026-21584

This High severity Improper Authorization vulnerability was introduced in versions 10.0.0, 10.1.0, 10.2.0, 11.0.0, 12.0.0, and 12.1.0 of Bamboo Data Center. This Improper Authorization vulnerability, with a CVSS Score of 7.6, allows an authenticated attacker to gain unintended access and can lead to the exposure of resources or functionality, possibly providing attackers with sensitive information or even execute arbitrary code. Atlassian recommends that Bamboo 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: * Bamboo Data Center 10.2: Upgrade to a release greater than or equal to 10.2.22 * Bamboo Data Center 12.1: Upgrade to a release greater than or equal to 12.1.10 See the release notes (https://confluence.atlassian.com/bambooreleases/bamboo-release-notes-1189793869.html). You can download the latest version of Bamboo Data Center from the download center (https://www.atlassian.com/software/bamboo/download-archives). This vulnerability was reported via our Penetration Testing program.

Published 2026-08-18 · last modified 2026-09-02.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.003 (21.5th percentile), scored 2026-10-03.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 22nd percentile — 21.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

Atlassian Bamboo
Atlassian Bamboo Data Center — versions 10.0.0 to 10.0.3, 10.1.0 to 10.1.1, 10.2.0 to 10.2.21

Weakness classification (CWE)

CWE-285 — Improper Authorization

References

confluence.atlassian.com/pages/viewpage.action (Vendor Advisory)
jira.atlassian.com/browse/BAM-26468 (Issue Tracking, Vendor Advisory)

Frequently asked questions

What is CVE-2026-21584?: CVE-2026-21584 is a high-severity vulnerability in Atlassian Bamboo, classified under Improper Authorization. CVSS score: 8.1/10. Published 2026-08-18.
How severe is CVE-2026-21584?: High severity. CVSS v3 base score is 8.1 out of 10.