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Confluence Data CenterApplication · Atlassian

CVE-2026-21577

MEDIUM · 6.5 CVSS v3.1 Developing Published 2026-07-21
Fix available
A fix is available. Upgrade to after 10.2.6 or later.
See remediation →
71/100
Remediation priority · Elevated
Remotely reachable Zero-click 4 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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 recommends that Confluence Data Center customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions: Confluence Data Center 9.2: Upgrade to a release greater than or equal to 9.2.17 Confluence Data Center 10.2: Upgrade to a release greater than or equal to 10.2.7 See the release notes ([https://confluence.atlassian.com/doc/confluence-release-notes-327.html]). You can download the latest version of Confluence Data Center from the download center ([https://www.atlassian.com/software/confluence/download-archives]). This vulnerability was reported via our Penetration Testing program.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · low confidence
Developing — this CVE was published recently and its authoritative NVD entry is still being established, so we're holding a technical summary until the source data settles rather than publish something unreliable. Re-checking after 2026-08-04.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Confluence Data CenterApplication
Affected:>= 9.0.1, <= 9.0.3>= 9.1.0, <= 9.1.1>= 9.2.0, <= 9.2.15>= 9.3.1, <= 9.3.2>= 9.4.0, <= 9.4.1>= 9.5.1, <= 9.5.4>= 10.0.2, <= 10.0.3>= 10.1.0, <= 10.1.2>= 10.2.0, <= 10.2.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to a release after 10.2.6
Recommended fix High confidence

Latest Confluence Data Center 9.2.x (minimum 9.2.17) or 10.2.x (minimum 10.2.7)

  1. Identify your current Confluence Data Center version from the Confluence administration console
  2. If running Confluence 9.2.x, upgrade to version 9.2.17 or later (preferably the latest 9.2.x release)
  3. If running Confluence 10.2.x, upgrade to version 10.2.7 or later (preferably the latest 10.2.x release)
  4. If running any other affected version (9.0.1, 9.1.0, 9.3.1, 9.4.0, 9.5.1, 10.0.2, 10.1.0), upgrade to the latest available version
  5. Before upgrading, back up your Confluence database and home directory
  6. Follow Atlassian's standard upgrade procedure for Confluence Data Center
  7. After upgrade, verify the Confluence instance is running correctly

Generated from the published advisory — verify against the referenced sources before acting.

We can identify the exact fixed release, upgrade, and verify it in staging — typical engagement from $1,600. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-21577 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data