CVE-2026-21577: This High severity DoS (Denial of Service) vulnerability was introduced in versions 9.0.1, 9.1.0, 9.2.0, 9.3.1

Routine

MEDIUM 6.5UPGRADE

CVE-2026-21577 is a medium-severity flaw (CVSS 6.5) affecting confluence data center. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

This High severity DoS (Denial of Service) vulnerability was introduced in versions 9.0.1, 9.1.0, 9.2.0, 9.3.1, 9.4.0, 9.5.1, 10.0.2, 10.1.0 and 10.2.0 of Confluence Data Center. This DoS (Denial of Service) vulnerability, with a CVSS Score of 7.1, allows an authenticated attacker to cause a resource to be unavailable for its intended users by temporarily or indefinitely disrupting services of a host connected to a network. Atlassian recomm

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 64%)
CISA exploited list	No
Weakness	CWE-400
Published	2026-07-21
Last modified	2026-10-24

Publisher (CNA): Atlassian · Vendor: atlassian

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-21 18:16 UTCPublished CVE record published
2026-10-24 19:10 UTCUpdated Record last modified

atlassian confluence data center UPGRADE

Affected: >= 9.0.1 and <= 9.0.3 · >= 9.1.0 and <= 9.1.1 · >= 9.2.0 and <= 9.2.15 · >= 9.3.1 and <= 9.3.2 · >= 9.4.0 and <= 9.4.1 · >= 9.5.1 and <= 9.5.4 · >= 10.0.2 and <= 10.0.3 · >= 10.1.0 and <= 10.1.2

Fixed in: newer than 10.2.6

Safe to downgrade to: a release before 9.0.1

1. Check installed version

apt-cache policy confluence-data-center || rpm -q confluence-data-center || confluence-data-center --version

2. UPGRADE to newer than 10.2.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade confluence-data-center

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade confluence-data-center

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 9.0.1 (Debian / Ubuntu)

apt-cache madison confluence-data-center sudo apt install confluence-data-center=<VERSION_BEFORE_9.0.1> sudo apt-mark hold confluence-data-center

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list confluence-data-center sudo dnf downgrade confluence-data-center-<VERSION_BEFORE_9.0.1> sudo dnf versionlock add confluence-data-center

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-21577?

confluence data center: upgrade to newer than 10.2.6. Exact commands for each OS are on this page.

Is CVE-2026-21577 being exploited?

CVE-2026-21577 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-21577 affect?

CVE-2026-21577 affects confluence data center. Severity is medium (CVSS 6.5). This High severity DoS (Denial of Service) vulnerability was introduced in versions 9.0.1, 9.1.0, 9.2.0, 9.3.1, 9.4.0, 9.5.1, 10.0.2, 10.1.0 and 10.2.0 of Confluence Data Center. This DoS (Denial of Service) vulnerability, with a CVSS Sc

How urgent is CVE-2026-21577?

Priority 32/100. No elevated risk signals yet.

Software pages

Atlassian Confluence vulnerabilities

Related CVEs

CVE-2026-21579 HIGH 7.5 UPGRADE This High severity Information Disclosure vulnerability was introduced in versions 7.17.0, 7.19.0, 8.5.0, 8.9.
CVE-2026-21589 HIGH 7.5 EXPLOITED UPGRADE UPGRADE Atlassian Multiple Products Files or Directories Accessible to External Parties Vulnerability

References

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