CVE-2026-21589: Atlassian Multiple Products Files or Directories Accessible to External Parties Vulnerability

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Atlassian Multiple Products. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-10-15, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-10-18; treat that as the outer limit, not the target.
• EPSS 12.7%, percentile 96: FIRST’s model estimates a 12.7% chance of exploitation activity in the next 30 days, higher than 96% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Editorial verdict: Act now. Atlassian Data Center File Read CVE-2026-21589 Exploited — Every self-managed Atlassian Data Center product is affected, a public detection script exists and CISA confirms exploitation; patch to a fixed LTS or block traversal patterns at the edge today.

What it is

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.

CISA’s summary

Multiple Atlassian products (Bitbucket Data Center ,Confluence Data Center, Jira Service Management Data Center, Jira Software Data Center, Bamboo Data Center, Crowd Data Center, Crucible and Fisheye) contain a files or directories accessible to external parties vulnerability which could allow an unauthenticated attacker to access specific files within the web application root directory in affected versions.

Weakness type: CWE-552.

Product: Atlassian Multiple Products · Assigned by: atlassian · Published: 2026-10-05

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2026-10-15; federal due date 2026-10-18. Known ransomware use: Unknown.
• CISA required action: 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.
• CISA SSVC assessment: exploitation active, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 12.71% probability of exploitation activity in the next 30 days; percentile 96.

Timeline

• 2026-10-05 — CVE record published by atlassian
• 2026-10-05 — erroneo.us brief: Atlassian Data Center File Read CVE-2026-21589 Exploited
• 2026-10-15 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2026-10-18 — CISA remediation deadline for US federal agencies
• 2026-10-19 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (confluence.atlassian.com) confluence.atlassian.com

Vulnerability records

1. CVE.org record CVE-2026-21589 cve.org
2. NVD entry CVE-2026-21589 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov
2. Listed in CISA KEV notes (cisa.gov) cisa.gov
3. Listed in CISA KEV notes (cisa.gov) cisa.gov

Other references from the CVE record and advisory

1. jira.atlassian.com jira.atlassian.com
2. jira.atlassian.com jira.atlassian.com
3. jira.atlassian.com jira.atlassian.com
4. jira.atlassian.com jira.atlassian.com
5. jira.atlassian.com jira.atlassian.com
6. jira.atlassian.com jira.atlassian.com
7. jira.atlassian.com jira.atlassian.com
8. jira.atlassian.com jira.atlassian.com
9. github.com github.com

All exploited Atlassian vulnerabilities · Today’s Security Digest