# What is CVE-2026-21589?

> CVE-2026-21589 is a critical-severity flaw (CVSS 9.3) in the software it affects, published on 5 October 2026. It is on the list of flaws known to be exploited, so criminals are already using it. The latest forecast puts its chance of use in the next 30 days at 13%. If you run an affected version, patch it first.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2026-21589

## At a glance

- **Verdict:** Fix this now. Attackers are using this flaw today. If you run an affected version, it goes to the top of your list.
- **Precursor Intelligence risk score:** 90 out of 100 (Critical); action: Emergency patch. Kept up to date as the evidence changes.
- **Severity:** Critical (CVSS 9.3 out of 10)
- **Known to be exploited:** Yes, it is on the government list of flaws known to be exploited
- **Chance of use in the next 30 days:** 13% (latest exploit-likelihood forecast)
- **Published:** 5 October 2026
- **Record last updated:** 7 October 2026
- **Affected products:** 0

## What is CVE-2026-21589? In plain terms

It can be attacked from anywhere on the internet without logging in, and nobody has to click anything.

### The official description

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.

### What kind of flaw is it?

- CWE-552: Files or Directories Accessible to External Parties

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- How hard it is to pull off: Easy: no special conditions
- Login needed first: No login needed
- Does someone have to click: No, nobody has to do anything

Severity 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`

## Is CVE-2026-21589 being exploited? Yes

Attackers are already using it. It is on the government list of flaws known to be exploited, and the latest forecast puts the chance of it being used in the next 30 days at 13%.

Exploit likelihood over the last 7 days: 1.8%, 1.8%, 2.8%, 2.8%, 2.8%, 2.8%, 13%.

### Timeline

- 5 October 2026: Published
- 7 October 2026: Record last updated
- 16 October 2026: Added to the known-exploited list

### How Precursor Intelligence ranks it

CVE-2026-21589 scores **90 out of 100 (Critical)**, with the action "Emergency patch".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: smaller factor
- Threat activity around it: smaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2026-21589?

No affected products have been listed for this flaw yet.

## How do I fix CVE-2026-21589?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the latest update from the vendor. The references list where the vendor has published details.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Check it wasn’t used before you patched.** Because criminals are already using this flaw, look for signs of a break-in on affected systems using the vendor’s guidance.

### References

- [jira.atlassian.com](https://jira.atlassian.com/browse/BAM-26567)
- [jira.atlassian.com](https://jira.atlassian.com/browse/BSERV-20604)
- [jira.atlassian.com](https://jira.atlassian.com/browse/CONFSERVER-104488)
- [jira.atlassian.com](https://jira.atlassian.com/browse/CRUC-8741)
- [jira.atlassian.com](https://jira.atlassian.com/browse/CWD-6610)
- [jira.atlassian.com](https://jira.atlassian.com/browse/FE-7583)
- [jira.atlassian.com](https://jira.atlassian.com/browse/JRASERVER-79546)
- [jira.atlassian.com](https://jira.atlassian.com/browse/JSDSERVER-16809)
- [github.com](https://github.com/watchtowrlabs/watchTowr-vs-Atlassian-CVE-2026-21589)

## Questions

### What is CVE-2026-21589?

CVE-2026-21589 is a critical-severity flaw in the software it affects, published on 5 October 2026. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything.

### How serious is CVE-2026-21589?

It scores 9.3 out of 10 on the CVSS severity scale, which is critical. Our risk score for CVE-2026-21589 is 90 out of 100, which is Critical. Its action is "Emergency patch". Attackers are using this flaw today. If you run an affected version, it goes to the top of your list.

### Is CVE-2026-21589 being exploited?

Attackers are already using it. It is on the government list of flaws known to be exploited, and the latest forecast puts the chance of it being used in the next 30 days at 13%.

### How do I fix CVE-2026-21589?

Install the update the vendor names in its advisory. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet. Because criminals are already using it, also check affected systems for signs of a break-in.

## Does CVE-2026-21589 affect you?

Precursor Intelligence keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

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