SecuritySense
HIGHvulnerability·

CVE-2026-21589: Atlassian Data Center Arbitrary File Read Vulnerability

An unauthenticated arbitrary file read vulnerability (CVE-2026-21589) affects multiple Atlassian Data Center products, allowing attackers to access specific files within the web application root directory. Exploitation requires prior knowledge of the target file’s exact name and path, but can lead to the disclosure of sensitive information. Active exploitation of this vulnerability has been reported.

This report was researched and drafted by an AI agent and reviewed by a human analyst prior to publication. View the agent workflow →

Overview

CVE-2026-21589 is an arbitrary file access vulnerability impacting multiple Atlassian Data Center products, including Bitbucket, Confluence, Jira Software, Jira Service Management, Bamboo, Crowd, Crucible, and Fisheye. This flaw allows an unauthenticated attacker to read specific files from the web application root directory. Given reports of active exploitation, immediate patching is critical for affected organizations.

Technical Analysis

  • Vulnerability: CWE-552 (Files or Directories Accessible to External Parties). An unauthenticated attacker can access specific files within the web application root directory.
  • Affected Products & Versions:
    • Bitbucket Data Center: introduced in >= 4.6.0, vulnerable up to < 9.4.26, < 10.2.8, < 10.5.1
    • Confluence Data Center: introduced in >= 5.10.0, vulnerable up to < 9.2.26, < 10.2.19
    • Crowd Data Center: introduced in >= 2.11.0, vulnerable up to < 6.3.7, < 7.0.3, < 7.1.7, < 7.2.4
    • Jira Software Data Center: introduced in >= 7.1.0, vulnerable up to < 9.12.40, < 10.3.26, < 11.3.12
    • Jira Service Management Data Center: introduced in >= 3.1.0, vulnerable up to < 5.12.40, < 10.3.26, < 11.3.12
    • Bamboo Data Center: introduced in >= 7.0.1, vulnerable up to < 10.2.24, < 12.1.12
    • Crucible: vulnerable up to < 4.9.15
    • Fisheye: vulnerable up to < 4.9.15
  • Attack Vector: Network (AV:N). Exploitation is remote and unauthenticated (PR:N).
  • Prerequisites: The attacker must have prior knowledge of the exact filename and path of the target file. The vulnerability does not allow directory enumeration.
  • Impact: Confidentiality (C:H). Successful exploitation can lead to the disclosure of sensitive files, potentially including configuration files, credentials, or other proprietary data. Integrity and Availability are not directly impacted (I:N, A:N).
  • CVSS v3.1 Score: 7.5 (High) – CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

Detection

  • Web Server Access Logs: Monitor web server access logs (e.g., Apache, Nginx, IIS) for GET requests to known sensitive files or file types within the Atlassian application’s web root that are not typically served publicly.
    • Look for requests to configuration files such as dbconfig.xml, atlassian-user.xml, server.xml, web.xml, setenv.sh, setenv.bat, application.properties, application.yml.
    • Look for requests to backup files (.bak, .zip, .sql) or log files (.log, catalina.out, .env) directly within the web application root or common subdirectories.
    • Analyze sc-status codes for successful (200) or unusual (e.g., 403, 404 for files that should exist but not be accessible) access attempts to these paths.
  • Network Intrusion Detection Systems (NIDS): Deploy NIDS rules to identify HTTP GET requests targeting specific sensitive file paths associated with Atlassian products.

Sigma Detection Rules

⚠️ AI-generated detection rules. These are experimental starting points. Review field names, EventIDs, and logic against your environment’s schema before deploying. Tune to reduce false positives.

Atlassian Data Center – Suspicious Configuration File Access (CVE-2026-21589)

title: Atlassian Data Center - Suspicious Configuration File Access (CVE-2026-21589)
id: 75751911-c918-4a6c-9418-866415779496
status: experimental
description: Detects unauthenticated attempts to access sensitive Atlassian or Java web application configuration files via CVE-2026-21589.
logsource:
  category: webserver
detection:
  selection:
    cs-method: 'GET'
    cs-uri-stem|endswith:
      - 'dbconfig.xml'
      - 'atlassian-user.xml'
      - 'server.xml'
      - 'web.xml'
      - 'setenv.sh'
      - 'setenv.bat'
      - 'application.properties'
      - 'application.yml'
      - 'config.xml'
      - 'settings.xml'
  condition: selection
level: high

Atlassian Data Center – Suspicious Log or Backup File Access (CVE-2026-21589)

title: Atlassian Data Center - Suspicious Log or Backup File Access (CVE-2026-21589)
id: 02d44e54-4f0e-4a11-8c4b-149d6837895e
status: experimental
description: Detects unauthenticated attempts to access sensitive log, backup, or environment files within the web application root via CVE-2026-21589.
logsource:
  category: webserver
detection:
  selection:
    cs-method: 'GET'
    cs-uri-stem|endswith:
      - '.log'
      - '.bak'
      - '.zip'
      - '.sql'
      - '.env'
      - 'catalina.out'
  condition: selection
level: medium

Mitigations

  1. Patch Immediately: Apply the latest security patches for all affected Atlassian Data Center products. Refer to the Atlassian advisories linked in the references for specific fix versions.
    • Bitbucket Data Center: Upgrade to 9.4.26, 10.2.8, 10.5.1 or later.
    • Confluence Data Center: Upgrade to 9.2.26, 10.2.19 or later.
    • Crowd Data Center: Upgrade to 6.3.7, 7.0.3, 7.1.7, 7.2.4 or later.
    • Jira Software Data Center: Upgrade to 9.12.40, 10.3.26, 11.3.12 or later.
    • Jira Service Management Data Center: Upgrade to 5.12.40, 10.3.26, 11.3.12 or later.
    • Bamboo Data Center: Upgrade to 10.2.24, 12.1.12 or later.
    • Crucible: Upgrade to 4.9.15 or later.
    • Fisheye: Upgrade to 4.9.15 or later.
  2. Restrict File Access: Ensure proper file system permissions are in place, limiting read access to sensitive configuration and data files to only the necessary service accounts.
  3. Network Segmentation: Isolate Atlassian Data Center instances from direct internet exposure where possible, placing them behind reverse proxies or web application firewalls (WAFs) that can filter suspicious requests.
  4. Monitor Logs: Continuously monitor web server and application logs for suspicious access patterns to sensitive files.

References

  • https://nvd.nist.gov/vuln/detail/CVE-2026-21589
  • https://jira.atlassian.com/browse/BAM-26567
  • https://jira.atlassian.com/browse/BSERV-20604
  • https://jira.atlassian.com/browse/CONFSERVER-104488
  • https://jira.atlassian.com/browse/CRUC-8741
  • https://jira.atlassian.com/browse/CWD-6610
  • https://jira.atlassian.com/browse/FE-7583
  • https://jira.atlassian.com/browse/JRASERVER-79546
  • https://jira.atlassian.com/browse/JSDSERVER-16809
  • https://www.securityweek.com/attackers-target-critical-atlassian-vulnerability-within-hours-of-poc-publication/
  • https://previdian.com/CVE-2026-21589
  • https://labs.watchtowr.com/you-wont-hear-about-these-even-in-myths-atlassian-jira-confluence-and-more-pre-auth-arbitrary-file-read-cve-2026-21589/
  • https://thehackernews.com/2026/10/atlassian-data-center-flaw-draws.html
  • https://github.com/watchtowrlabs/watchTowr-vs-Atlassian-CVE-2026-21589
  • https://www.bleepingcomputer.com/news/security/hackers-exploit-critical-atlassian-flaw-after-public-poc-release/

Indicators of Compromise

No public IOCs available at time of writing.

MITRE ATT&CK

  • T1190 — Exploit Public-Facing Application
  • T1083 — File and Directory Discovery
  • T1552.001 — Credentials In Files
🤖 AI Attribution
Generated by gemini-2.5-flash ·
3,117 input / 2,588 output tokens ·
Reviewed and approved by a human analyst before publication
#vulnerability#active-exploitation#arbitrary-file-read#atlassian#cve#data-center#high#pre-auth#vulnerability