CVE-2025-66402: Misskey is an open source, federated social media platform

Routine

MEDIUM 6.5UPGRADE

CVE-2025-66402 is a medium-severity flaw (CVSS 6.5) 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. Starting in version 13.0.0-beta.16 and prior to version 2025.12.0, an actor who does not have permission to view favorites or clips can can export the posts and view the contents. Version 2025.12.0 fixes the issue.

Why this priority

Public exploit reference

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	0.3% (top 76%)
CISA exploited list	No
Weakness	CWE-862
Published	2025-12-16
Last modified	2026-10-14

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

Last updated 2026-10-14 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-12-16 00:16 UTCPublished CVE record published
2026-10-14 13:10 UTCUpdated Record last modified

misskey misskey UPGRADE

Affected: >= 13.1.0 and < 2025.12.0 · 13.0.0 · 13.0.0 beta16 · 13.0.0 beta21 · 13.0.0 beta22 · 13.0.0 beta23 · 13.0.0 beta24 · 13.0.0 beta25

Fixed in: 2025.12.0

Safe to downgrade to: a release before 13.0.0

1. Check installed version

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

2. UPGRADE to 2025.12.0 (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 13.0.0 (Debian / Ubuntu)

apt-cache madison misskey sudo apt install misskey=<VERSION_BEFORE_13.0.0> 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_13.0.0> 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-2025-66402?

misskey: upgrade to 2025.12.0. Exact commands for each OS are on this page.

Is CVE-2025-66402 being exploited?

CVE-2025-66402 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-2025-66402 affect?

CVE-2025-66402 affects misskey. Severity is medium (CVSS 6.5). Misskey is an open source, federated social media platform. Starting in version 13.0.0-beta.16 and prior to version 2025.12.0, an actor who does not have permission to view favorites or clips can can export the posts and view the contents.

How urgent is CVE-2025-66402?

Priority 34/100. Public exploit reference

Related CVEs

CVE-2025-66482 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-2026-28431 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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