How severe is CVE-2026-21589?

No CVSS score has been assigned to CVE-2026-21589 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-21589?

Affected package information for CVE-2026-21589 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2026-21589?

No fixed release is recorded for CVE-2026-21589 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

How do I detect CVE-2026-21589 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2026-21589 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-21589 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-21589 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-21589?

CVE-2026-21589 has an EPSS (Exploit Prediction Scoring System) score of 2.8%, placing it in the 86th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Is CVE-2026-21589 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2026-21589 (Atlassian Multiple Products Files or Directories Accessible to External Parties Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-10-15. CISA required all US federal civilian agencies to remediate this vulnerability by 2026-10-18. The required action was: 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. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2026-21589?

CVE-2026-21589 is classified as CWE-552 (CWE-552). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2026-21589?

A Nuclei detection template exists for CVE-2026-21589, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2026-21589 published, and has it been updated?

CVE-2026-21589 was published on October 5, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV · ACTIVELY EXPLOITED

CVE-2026-21589 — Atlassian

CVE-2026-21589 is a CWE-552 vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-10-15) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

h3. Summary 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…

Published

Oct 5, 2026

Updated

Oct 5, 2026

Affected

9 products

Patched

See advisory

Exploits

None indexed

Exploitation data as of Oct 15, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-10-15. Federal agencies were required to remediate by 2026-10-18.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2026-21589.

EPSS Exploitation Probability

via FIRST.org ↗

2.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs86th percentile — riskier than 86% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Description

h3. Summary

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.

h3. Context

This vulnerability allows an unauthenticated remote attacker to access specific files within the web application root directory in affected versions.

h3. Details:

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, 7.1.1, 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.

Affected Products

9 products · 20 configurations

Application

bambooatlassian

≥ 11.0.0 && < 12.1.12

range

Application

bitbucket data centeratlassian

≥ 10.3.0 && < 10.5.1

range

Application

bitbucket serveratlassian

≥ 4.6.0 && ≤ 8.14.6

range

Application

confluence data centeratlassian

≥ 9.3.0 && < 10.2.19

range

Application

crowdatlassian

≥ 7.2.0 && < 7.2.4

range

Application

crucibleatlassian

< 4.9.15

range

Detection & mitigation playbook

Vulnerability

Detect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Remediation status
No fixed release is recorded for CVE-2026-21589 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How to detect CVE-2026-21589

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2026-21589 -u https://target

Template: Atlassian Jira/Confluence/Bitbucket - Pre-Auth Arbitrary File Read
Severity: critical
Impact: An unauthenticated attacker can read arbitrary files within the Tomcat application context, including WEB-INF configuration files. When Atlassian Crowd is configured, this can leak plaintext credentials from crowd.properties, enabling full administrative access to the identity management system and all connected Atlassian products.
Remediation: Update to the fixed versions: Jira 9.12.40/10.3.26/11.3.12, Confluence 9.2.26/10.2.19, Bitbucket 9.4.26/10.2.8/10.5.1, Bamboo 10.2.24/12.1.12, Crowd 6.3.7/7.0.3/7.1.7/7.2.4, Crucible 4.9.15, Fisheye 4.9.15.

Template by ProjectDiscovery nuclei-templates (Kazgangap, DhiyaneshDk, watchtowr), MIT licensed. View the full template. Scan only systems you are authorised to test.

Frequently Asked Questions

h3. Summary 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

O3 Security · Impact-Aware SCA

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CVE-2026-21589 — Atlassian

Exploitation Status

Actively exploited in the wild

EPSS Exploitation Probability

Description

Affected Products

Detection & mitigation playbook

Detect

Remediation status

Mitigate without a patch

How to detect CVE-2026-21589

Frequently Asked Questions

Is CVE-2026-21589 in your dependencies?