How to fix CVE-2026-21589: Atlassian Multiple Products (exploited in the wild)

This is a vulnerability in Bitbucket Data Center, Confluence Data Center, Jira Service Management Data Center, Jira Software Data Center, Bamboo Data Center. Crowd Data Center, Crucible and Fisheye. This Arbitrary File Access vulnerability allows an unauthenticated attacker to access specific files within the web application root directory in affected versions. Exploitation requires prior knowledge of the target file's exact name and path; this vulnerability does not allow attackers to enumerate or list directory contents. In some configurations, there may be some sensitive files that make this highly severe. This vulnerability allows an unauthenticated remote attacker to access specific files within the web application root directory in affected versions. The vulnerability must be addressed for affected versions of: -- Bitbucket Data Center, introduced in version >= 4.6.0, fix versions: 9.4.26, 10.2.8, 10.5.1 -- Confluence Data Center, introduced in version >= 5.10.0, fix versions 9.2.26, 10.2.19 -- Crowd Data Center, introduced in version >= 2.11.0, fix versions 6.3.7, 7.0.3, 7.1.7, 7.2.4 -- Jira Software Data Center, introduced in version >= 7.1.0, fix versions 9.12.40, 10.3.26, 11.3.12 -- Jira Service Management Data Center, introduced in version >= 3.1.0, fix versions 5.12.40, 10.3.26, 11.3.12 -- Bamboo Data Center >= 7.0.1, fix versions 10.2.24, 12.1.12 -- Crucible, fix versions 4.9.15 -- Fisheye, fix version 4.9.15 -- Exploitation requires prior knowledge of the target file's exact name and path. The vulnerability does not include the capability to enumerate or list directory contents.

• Severity: CRITICAL (CVSS 4.0 9.3, vector CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:H).
• Weakness: CWE-552.
• NVD published 2026-10-05, status Analyzed.

Anyone running Atlassian Multiple Products in the version ranges below. Internet-facing instances are the priority.

• atlassian bitbucket data center: from 7.17.0 up to (not including) 9.4.26.
• atlassian bitbucket data center: from 9.5.0 up to (not including) 10.2.8.
• atlassian bitbucket data center: from 10.3.0 up to (not including) 10.5.1.
• atlassian confluence data center: from 5.10.0 up to (not including) 9.2.26.
• atlassian confluence data center: from 9.3.0 up to (not including) 10.2.19.
• atlassian crowd: from 2.11.0 up to (not including) 6.3.7.
• atlassian crowd: from 7.0.0 up to (not including) 7.0.3.
• atlassian crowd: from 7.1.0 up to (not including) 7.1.7.
• atlassian crowd: from 7.2.0 up to (not including) 7.2.4.
• atlassian jira data center: from 7.1.0 up to (not including) 9.12.40.
• atlassian bitbucket server: from 4.6.0 up to and including 8.14.6.
• atlassian jira service desk: from 3.1.0 up to and including 4.13.27.

Version ranges come from the NVD CPE configuration. Confirm against the vendor advisory before you rely on them.

• Exploited in the wild: added to the CISA Known Exploited Vulnerabilities catalog on 2026-10-15; federal remediation due date 2026-10-18.
• Public proof-of-concept code: 13 GitHub repositories from 13 accounts, the first on 2026-10-06.

• EPSS (probability of exploitation activity in the next 30 days): 12.71%, higher than 96% of all scored CVEs (as of 2026-10-24).
• CVERadar threat level: 65/100 (see methodology).
• Likely ATT&CK techniques: T1190 Exploit Public-Facing Application (inferred).

1. Find every instance. List where Atlassian Multiple Products runs, including test, DR and forgotten internet-facing systems, and record the installed version.
2. Upgrade to a fixed release. atlassian bitbucket data center: 9.4.26 or later; atlassian bitbucket data center: 10.2.8 or later; atlassian bitbucket data center: 10.5.1 or later; atlassian confluence data center: 9.2.26 or later. Get the build from the vendor advisory.
3. If you can't patch today, follow CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
4. Verify the fix. Re-run the version check on every instance and confirm it reports the fixed build (9.4.26 or later). Re-scan from outside if the service is exposed.
5. Hunt for signs of earlier compromise. If the system was exposed before you patched, assume it may have been hit and check the items below.
6. Rotate credentials stored on or used by the affected system if you cannot rule out compromise, and keep the logs you reviewed.

Detection hints

• T1190 Exploit Public-Facing Application: Review WAF, reverse-proxy and application logs for unusual requests to Multiple Products (odd paths, oversized or encoded payloads, bursts of errors), going back to at least 2026-10-05.

Detection commands are generic starting points, not CVE-specific signatures. Use the indicators from the vendor advisory when it publishes them.

• NVD: CVE-2026-21589 nvd.nist.gov/vuln/detail/CVE-2026-21589
• CVE.org record www.cve.org/CVERecord?id=CVE-2026-21589
• Vendor link from CISA KEV confluence.atlassian.com/security/cve-2026-21589-arbitrary-file-access
• Mitigation, Vendor Advisory jira.atlassian.com/browse/BAM-26567
• Mitigation, Vendor Advisory jira.atlassian.com/browse/BSERV-20604
• Mitigation, Vendor Advisory jira.atlassian.com/browse/CONFSERVER-104488
• Mitigation, Vendor Advisory jira.atlassian.com/browse/CRUC-8741
• Mitigation, Vendor Advisory jira.atlassian.com/browse/CWD-6610
• Mitigation, Vendor Advisory jira.atlassian.com/browse/FE-7583
• Mitigation, Vendor Advisory jira.atlassian.com/browse/JRASERVER-79546
• CISA KEV catalog www.cisa.gov/known-exploited-vulnerabilities-catalog
• FIRST EPSS (2026-10-24) api.first.org/data/v1/epss?cve=CVE-2026-21589