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Atlassian Data Center products: Unauthenticated arbitrary file read

CVE-2026-21589Critical 9.3Actively exploitedPublic exploit

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Actively exploited – in the CISA catalogue of Known Exploited Vulnerabilities since 15 Oct 2026
Deadline for US federal agencies: 18 Oct 2026

Summary

Several self-hosted Atlassian Data Center products contain an arbitrary file access vulnerability (CVE-2026-21589). An unauthenticated remote attacker can read specific files within the web application root directory if the exact file name and path are known; directory listing is not possible. Sensitive files in some configurations can make the impact severe. CISA lists the vulnerability as known exploited.

Affected

  • Bitbucket Data Center: all versions before 9.4.26, 10.2.8 and 10.5.1 (fixed versions per branch)
  • Confluence Data Center: all versions before 9.2.26 and 10.2.19
  • Jira Software Data Center: all versions before 9.12.40, 10.3.26 and 11.3.12
  • Jira Service Management Data Center: all versions before 5.12.40, 10.3.26 and 11.3.12
  • Bamboo Data Center: all versions before 10.2.24 and 12.1.12
  • Crowd Data Center: all versions before 6.3.7, 7.0.3, 7.1.7 and 7.2.4
  • Crucible and Fisheye: all versions before 4.9.15
  • Atlassian Cloud sites are not affected.

Fixed in

  • Bitbucket Data Center: 9.4.26, 10.2.8, 10.5.1
  • Confluence Data Center: 9.2.26, 10.2.19
  • Jira Software Data Center: 9.12.40, 10.3.26, 11.3.12
  • Jira Service Management Data Center: 5.12.40, 10.3.26, 11.3.12
  • Bamboo Data Center: 10.2.24, 12.1.12
  • Crowd Data Center: 6.3.7, 7.0.3, 7.1.7, 7.2.4
  • Crucible and Fisheye: 4.9.15

Workaround

  • Remove internet access to affected instances until patched, as recommended by Atlassian.
  • Apply the Web Application Firewall rule published by Atlassian to block traversal patterns, or the Tomcat RewriteValve or urlrewrite.xml mitigation described in the Atlassian tickets.
  • Treat these mitigations as temporary; they are not a replacement for patching.

Exploitation

  • Exploited in the wild: yes. CISA added the vulnerability to its Known Exploited Vulnerabilities catalog on 15 October 2026.
  • Public proof-of-concept code: reports conflict on whether a working exploit has been published; assume one is available.
  • Escalation: in certain Crowd-integrated deployments, researchers showed the file read can lead to administrator access. Exposed credentials or configuration files should be treated as compromised.

Our recommendation

  • Patch all affected Data Center products to the fixed versions immediately.
  • Until patched, restrict external access to affected instances.
  • Review web access logs for traversal-style requests and check for new or unexpected administrator accounts.
  • If a compromise is possible, rotate credentials stored in configuration files, especially Crowd and application credentials.
  • Cloud customers require no action.

Public exploits

Links to third-party sites, not checked by us – exploit code can contain malware. Only use it in isolated test environments.

Research sources

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 30 Oct 2026, 13:30.

Original description (NVD)

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.

Required action (CISA)

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.

NVD references (10)

Sources

The tracker combines official, freely usable data sources – updated continuously:

This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.

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