CVE-2026-28431: Misskey is an open source, federated social media platform

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-28431 is a high-severity flaw (CVSS 7.5) affecting misskey. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 breac

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 82%)
CISA exploited list	No
Weakness	CWE-285
Published	2026-03-10
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: misskey

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-10 07:43 UTCPublished CVE record published
2026-06-17 10:28 UTCUpdated Record last modified

misskey misskey UPGRADE

Affected: >= 8.45.0 and < 2026.3.1

Fixed in: 2026.3.1

Safe to downgrade to: a release before 8.45.0

1. Check installed version

apt-cache policy misskey || rpm -q misskey || misskey --version

2. UPGRADE to 2026.3.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade misskey

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade misskey

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 8.45.0 (Debian / Ubuntu)

apt-cache madison misskey sudo apt install misskey=<VERSION_BEFORE_8.45.0> sudo apt-mark hold misskey

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

dnf --showduplicates list misskey sudo dnf downgrade misskey-<VERSION_BEFORE_8.45.0> sudo dnf versionlock add misskey

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-2026-28431?

misskey: upgrade to 2026.3.1. Exact commands for each OS are on this page.

Is CVE-2026-28431 being exploited?

CVE-2026-28431 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-2026-28431 affect?

CVE-2026-28431 affects misskey. Severity is high (CVSS 7.5). 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

How urgent is CVE-2026-28431?

Priority 36/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2025-66482 MEDIUM 6.5 UPGRADE Misskey is an open source, federated social media platform
CVE-2025-66402 MEDIUM 6.5 UPGRADE Misskey is an open source, federated social media platform
CVE-2026-28433 MEDIUM 4.3 UPGRADE Misskey is an open source, federated social media platform
CVE-2026-28432 HIGH 7.5 UPGRADE Misskey is an open source, federated social media platform
CVE-2025-25306 CRITICAL 9.3 UPGRADE Misskey is an open source, federated social media platform

References

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