# CVE-2026-21589 — Atlassian Bamboo Data Center

> As of 2026-10-06, CVE-2026-21589 is a Critical-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in Atlassian Bamboo Data Center, CVSS v4.0 9.3, EPSS 0.7% (53.0th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-21589, most recently “Atlassian Data Center critical unauthenticated arbitrary file access vulnerability (CVE-2026-21589) across Bitbucket, Confluence, Jira, Bamboo, Crowd, Crucible and Fisheye”.

**Last updated:** 2026-10-06

## What is CVE-2026-21589?

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.

The record classifies CVE-2026-21589 under weakness class [CWE-552](https://intel.threadlinqs.com/cwe/CWE-552). 8 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 5 days ago.

## Severity and exploitation probability

- **CVSS v4.0 base score:** 9.3 — Critical (derived from score) (`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`)
- **EPSS (FIRST):** 0.7% probability of exploitation in the next 30 days, higher than 53.0% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 9.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-10-05, last modified 2026-10-06

## Is CVE-2026-21589 being exploited?

Weaponised exploit code for CVE-2026-21589 is publicly available. 3 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (`http/cves/2026/CVE-2026-21589.yaml`).

- [MarcusProgram/CVE-2026-21589](https://github.com/MarcusProgram/CVE-2026-21589) (github)
- [watchtowrlabs/watchTowr-vs-Atlassian-CVE-2026-21589](https://github.com/watchtowrlabs/watchTowr-vs-Atlassian-CVE-2026-21589) (github)
- [tc4dy/CVE-2026-21589-PoC-Exploit](https://github.com/tc4dy/CVE-2026-21589-PoC-Exploit) (github)

## Affected products and versions

- [Atlassian](https://intel.threadlinqs.com/vendors/atlassian): Bamboo Data Center, Bitbucket Data Center, Confluence Data Center, Crowd Data Center, Crucible Data Center, Fisheye Data Center, Jira Service Management Data Center, Jira Software Data Center

## How to fix CVE-2026-21589

No vendor patch reference has been recorded for CVE-2026-21589 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-21589

1 tracked threat in the Threadlinqs corpus references CVE-2026-21589, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Atlassian Data Center critical unauthenticated arbitrary file access vulnerability (CVE-2026-21589) across Bitbucket, Confluence, Jira, Bamboo, Crowd, Crucible and Fisheye](https://intel.threadlinqs.com/threat/TL-2026-2966) — CRITICAL · 2026-10-06

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on 2026-10-07. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [jira.atlassian.com](https://jira.atlassian.com/browse/BAM-26567)
- [jira.atlassian.com (BSERV 20604)](https://jira.atlassian.com/browse/BSERV-20604)
- [jira.atlassian.com (CONFSERVER 104488)](https://jira.atlassian.com/browse/CONFSERVER-104488)
- [jira.atlassian.com (CRUC 8741)](https://jira.atlassian.com/browse/CRUC-8741)
- [jira.atlassian.com (CWD 6610)](https://jira.atlassian.com/browse/CWD-6610)

_Showing 5 of 8 recorded references._

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-21589
Full detection coverage and IOCs for threats exploiting CVE-2026-21589 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp