To check whether you are exposed to Atlassian’s unauthenticated file-read vulnerability, identify whether you run a self-managed product named in the advisory, note its installed version, and compare it with that product’s fixed-version thresholds below. Atlassian says all versions of the named products are affected. It says affected Cloud products have been patched and Cloud customers need take no action for this advisory.
Which Atlassian products are affected?
Atlassian’s CVE-2026-21589 security advisory, released and last modified on 5 October 2026, lists eight products. Its fixed versions are specific to each product and release line:
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| Product | Advisory fixed versions |
|---|---|
| Bitbucket Data Center | 9.4.26, 10.2.8, 10.5.1 |
| Confluence Data Center | 9.2.26, 10.2.19 |
| Jira Service Management Data Center | 5.12.40, 10.3.26, 11.3.12 |
| Jira Software Data Center | 9.12.40, 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 | 4.9.15 |
| Fisheye | 4.9.15 |
For an installation on one of the listed release lines, the corresponding version shown is the advisory’s fix threshold: that version or a later version in that line is fixed. Do not compare a version with another product’s threshold. Atlassian recommends upgrading to the fixed LTS release or later; check the live advisory and release notes to confirm the supported upgrade path before making a change.
How to check your installation
- Determine the deployment type. Identify whether each product is Atlassian Cloud or self-managed. The advisory says affected Cloud products have been patched and Cloud customers do not need to take action for this CVE. Check self-managed Data Center deployments against the table.
- Inventory each product and version. Record the product name and installed version for every instance. If your organization runs more than one listed product, check each separately; their thresholds differ.
- Compare each version with its product’s threshold. A version below the applicable fixed version is affected and needs action. A version at or above that threshold in the corresponding release line meets the advisory’s fix threshold.
- Check every cluster node. Inventory all nodes rather than relying on one server’s version, and apply any required mitigation to each node. For Bitbucket, follow the advisory’s instructions for mirrors where applicable.
- Check public reachability. Note whether an instance can be reached from the public internet. Public exposure affects triage and should inform interim access restrictions, even if the instance requires authentication.
What the vulnerability allows
Atlassian describes CVE-2026-21589 as arbitrary file access: an unauthenticated attacker can access specific files within the web application root directory on affected versions. The attacker needs prior knowledge of the target file’s exact name and path; the flaw does not allow directory listing or enumeration. Some configurations may contain sensitive files that increase risk.
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Atlassian rates the vulnerability Critical, with a CVSS 4.0 score of 9.3. That is the vendor’s severity assessment, not a measure of the exposure or impact of every individual installation.
What to do if a version is affected
Patch as soon as practical
Upgrade to the applicable fixed version or later, following Atlassian’s recommendation to use the fixed LTS release or later. Confirm the release path for your product and deployment in the current advisory and release notes before upgrading.
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Restrict access while patching is delayed
If you cannot patch immediately, Atlassian recommends removing the instance from the internet where possible or restricting external network access until you can take action. An authentication requirement does not make public reachability irrelevant to this vulnerability.
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Atlassian provides a traversal-pattern regular expression for use in a web application firewall or proxy, as well as product-specific configuration options: Tomcat RewriteValve for Confluence, Jira Service Management, Jira Software, Bamboo, and Crowd; and a urlrewrite.xml rule for Bitbucket. These changes depend on product, version, and deployment. Follow the advisory’s instructions, back up configuration files, apply cluster steps to every node (and Bitbucket mirrors where applicable), and test URL-encoded cases as directed.
How to investigate possible exploitation
Atlassian says it cannot confirm whether customer instances have been affected and recommends engaging your local security team. Review access logs for suspicious traversal requests. The advisory says to URL-decode each request line up to two decoding passes and look for .. immediately adjacent to /, \, or ::; alternatively, search raw lines with the regular expression in the advisory.
A matching request is a reason to investigate, not proof that a file was successfully read or that the instance was compromised. Work with your security team to assess the request and relevant system evidence.
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Does this affect Atlassian Cloud?
Atlassian says its affected Cloud products have been patched and Cloud customers do not need to take action for CVE-2026-21589. The advisory applies to the named self-managed products and versions listed above. For any deployment whose status is unclear, consult the live Atlassian advisory.
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