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MisskeyApplication

CVE-2026-28431

HIGH · 7.5 CVSS v3.1 Published 2026-03-10
Fix available
A fix is available. Upgrade to 2026.3.1 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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
Misskey is an open source, federated social media platform. All Misskey servers running versions 8.45.0 and later, but prior to 2026.3.1, contain a vulnerability that allows bad actors access to data that they ordinarily wouldn't be able to access due to insufficient permission checks and proper input validation. This vulnerability occurs regardless of whether federation is enabled or not. This vulnerability could lead to a significant data breach. This vulnerability is fixed in 2026.3.1.

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 · moderate confidence

Misskey versions 8.45.0 through 2026.3.0 contain an authorization bypass vulnerability caused by insufficient permission checks and improper input validation. This allows authenticated or unauthenticated actors to access sensitive data outside their intended permissions, independent of federation settings.

MitigationUpgrade Misskey to version 2026.3.1 or later to apply the security patch addressing the permission and input validation flaws.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

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
MisskeyApplication
Affected:>= 8.45.0, < 2026.3.1

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
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Confirm Misskey is running
    Identify if Misskey is deployed in your environment by checking running processes, container images, or the web service responding on the expected port (default 3000)
    Affected if Misskey is not present in your environment, this CVE does not apply
  2. Locate Misskey version information
    Check the installed Misskey instance version by querying the /api/v1/instance/info endpoint, reviewing package.json in the installation directory, or accessing the admin panel's system information page
    Affected if Unable to determine the version indicates Misskey may not be properly installed or accessible
  3. Compare installed version against affected range
    Match your identified version number to the vulnerable range: versions 8.45.0 through 2026.3.0 are affected. Versions below 8.45.0 or at/above 2026.3.1 are not affected
    Affected if Your installed version falls within >= 8.45.0 and < 2026.3.1, indicating your environment is vulnerable to the authorization bypass

Your environment is affected by CVE-2026-28431 if Misskey is running and the installed version is 8.45.0 or higher but lower than 2026.3.1, regardless of federation settings.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 2026.3.1 or later
Fixed in 2026.3.1
Interim mitigation

Upgrade Misskey to version 2026.3.1 or later to apply the security patch addressing the permission and input validation flaws.

Recommended fix Moderate confidence

2026.3.1

  1. Backup your Misskey installation and database before proceeding with any upgrade
  2. Identify your current Misskey version (check package.json or run misskey version)
  3. Upgrade Misskey to version 2026.3.1 using your package manager (e.g., npm, yarn, or pnpm depending on your setup)
  4. Restart the Misskey service after the upgrade completes
  5. Verify the upgrade was successful by checking the running version matches 2026.3.1
  6. Test that the authorization behavior is corrected and the application functions normally

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

Fix this in Misskey Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
25.0 hours of engineering $4,400
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,040.

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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-2026-28431 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