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CVE-2026-21589

CRITICAL 9.3 KNOWN EXPLOITED PoC CATALOGUED DETECTION TEMPLATE

Published 2026-10-05 · Last modified 2026-10-19

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.

ACTIVELY EXPLOITED

Confirmed exploited in the wild — in CISA KEV since 2026-10-15. Patch or mitigate now.

Exploitation likelihood

99.5%chance of exploitation in 30 days · 100th percentile

● In CISA KEV (2026-10-15) ● Catalogued PoC

Impact if exploited

9.3CVSS 4.0 · CRITICAL

  • ConfidentialityHigh
  • IntegrityNone
  • AvailabilityNone

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable
  • ✓Requirements: No special attack requirements

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

Public PoC or exploit resources are catalogued below.

Listed by the named source; Vulnpedia has not tested these resources.

PoC data: JSON

Detection templates

Detection checks are listed separately from PoCs.

Resource commands

nuclei -id CVE-2026-21589 -u https://TARGETDetection template — review its checks and affected versions before use.
curl -s https://vulnpedia.com/cve/CVE-2026-21589/poc.jsonMachine-readable PoC index for this CVE (for automation).

Search for new PoCs

Search GitHub now — results may be empty or unverified.

Tracked sources are checked daily for recent CVEs, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Data snapshot:

Affected

Vendors Atlassian

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 Bitbucket Server Crowd Jira Data Center Jira Service Desk

Weakness (CWE)

  • CWE-552: Files or Directories Accessible to External Parties

CVSS 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

References and research data (JSON)

Unverified PoC candidates

Catalogue matches for further research. These repositories have not been validated as working exploits.

13 candidates

Additional exploitation reports

Source-specific reports, separate from CISA KEV. Repeated observations from one source are not independent confirmations.

  • VulnCheck KEV · 2026-10-07T00:00:00Z

    Source guidance: 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.

    Source ransomware assessment: Unknown

    VulnCheck KEV · CVE-2026-21589 · Updated 2026-10-07T00:00:00Z
  • VulnCheck KEV · 2026-10-07T00:00:00ZVulnCheck KEV · CVE-2026-21589
  • VulnCheck KEV · 2026-10-15T00:00:00ZVulnCheck KEV · CVE-2026-21589
  • VulnCheck KEV · 2026-10-22T00:00:00ZVulnCheck KEV · CVE-2026-21589
  • VulnCheck KEV · 2026-10-22T00:00:00ZVulnCheck KEV · CVE-2026-21589
  • VulnCheck KEV · 2026-10-23T00:00:00ZVulnCheck KEV · CVE-2026-21589
  • VulnCheck KEV · 2026-10-24T00:00:00ZVulnCheck KEV · CVE-2026-21589
  • VulnCheck KEV · 2026-10-25T00:00:00ZVulnCheck KEV · CVE-2026-21589
  • VulnCheck KEV · 2026-10-25T00:00:00ZVulnCheck KEV · CVE-2026-21589

Known Affected Software Configurations

VendorProductVersion range
AtlassianBitbucket Data Center≥ 7.17.0 and < 9.4.26
AtlassianBitbucket Data Center≥ 9.5.0 and < 10.2.8
AtlassianBitbucket Data Center≥ 10.3.0 and < 10.5.1
AtlassianBitbucket Server≥ 4.6.0 and ≤ 8.14.6
AtlassianConfluence Data Center≥ 5.10.0 and < 9.2.26
AtlassianConfluence Data Center≥ 9.3.0 and < 10.2.19
AtlassianCrowd≥ 2.11.0 and < 6.3.7
AtlassianCrowd≥ 7.0.0 and < 7.0.3
AtlassianCrowd≥ 7.1.0 and < 7.1.7
AtlassianCrowd≥ 7.2.0 and < 7.2.4
AtlassianJira Data Center≥ 7.1.0 and < 9.12.40
AtlassianJira Data Center≥ 9.13.0 and < 10.3.26
AtlassianJira Data Center≥ 10.4.0 and < 11.3.12
AtlassianJira Service Desk≥ 3.1.0 and ≤ 4.13.27
AtlassianJira Service Management≥ 4.14.0 and < 5.12.40
AtlassianJira Service Management≥ 5.13.0 and < 10.3.26
AtlassianJira Service Management≥ 10.4.0 and < 11.3.12
AtlassianBamboo≥ 7.0.1 and < 10.2.24
AtlassianBamboo≥ 11.0.0 and < 12.1.12
AtlassianCrucible< 4.9.15
AtlassianFisheye< 4.9.15

All CVSS metrics

  • CRITICAL 9.3 v4.0 · CNA Primary
    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
  • CRITICAL 9.3 v4.0 · NVD Secondary
    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
  • HIGH 7.5 v3.1 · NVD Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

Exploit-tagged references (not proof of a PoC)

Patches & mitigations

Advisories

Technical & other

Sources: NVD · CVE.org · EPSS