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Known exploited vulnerability

CVE-2026-21589

criticalCVSS 4.0 9.3In CISA KEVEPSS 100%Published · Atlassian

The short answer

CVE-2026-21589 affects Atlassian Bamboo Data Center and is rated critical (CVSS 9.3). CISA added it to the Known Exploited Vulnerabilities catalog on 2026-10-15: attackers are using it, so patch it first.

What it is

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.

Weakness: CWE-552.

Severity

9.3 critical

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Exploited (CISA KEV)

Yes, since Oct 15, 2026

Federal due date Oct 18, 2026

EPSS, next 30 days

100%

Higher than 100% of scored CVEs

How it can be exploited

Attack vector
Network
Attack complexity
Low
Attack requirements
None
Privileges required
None
User interaction
None
Confidentiality impact
High
Integrity impact
None
Availability impact
None

What CISA says to do

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…

Affected products

Bamboo Data Center, Bitbucket Data Center, Confluence Data Center, Crowd Data Center, Crucible Data Center, Fisheye Data Center, Jira Service Management Data Center, Jira Software Data Center. NVD's record lists the exact affected versions.

References

Questions

Is CVE-2026-21589 being exploited?

Yes. CISA added CVE-2026-21589 to its Known Exploited Vulnerabilities catalog on 2026-10-15, with a federal remediation due date of 2026-10-18.

How do I fix CVE-2026-21589?

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…

From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Analyzed. The description is NVD's text, quoted as published.

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