The US Cybersecurity and Infrastructure Security Agency (CISA) added CVE-2026-21589, a Atlassian Multiple Products Files or Directories Accessible to External Parties Vulnerability, to its Known Exploited Vulnerabilities (KEV) catalog on October 15, 2026. CISA adds a flaw to the catalog when it has reliable evidence that attackers are exploiting it in the wild.
What CISA says
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.
— CISA KEV catalog entry for CVE-2026-21589
Key facts
| CVE | CVE-2026-21589 |
|---|---|
| Vendor / product | Atlassian Multiple Products |
| Added to KEV | October 15, 2026 |
| Federal deadline | October 18, 2026 |
| Known ransomware use | Unknown |
| Weakness (CWE) | CWE-552 |
| CISA forensic triage | Yes |
| CVSS base score (NVD) | 9.3 Critical |
| 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/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 |
Who has to act, and by when
US federal civilian executive branch agencies are required to remediate the vulnerability by October 18, 2026. CISA urges all organizations to prioritize KEV-listed flaws as part of their vulnerability management.
CISA’s required action for this entry:
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.
References
- CISA Known Exploited Vulnerabilities Catalog https://www.cisa.gov/known-exploited-vulnerabilities-catalog
- NIST NVD — CVE-2026-21589 https://nvd.nist.gov/vuln/detail/CVE-2026-21589
- confluence.atlassian.com https://confluence.atlassian.com/security/cve-2026-21589-arbitrary-file-access-vulnerability-impacts-multiple-products-1870495748.html?ref=labs.watchtowr.com
- www.cisa.gov https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- www.cisa.gov https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk