CVE-2026-28431 Misskey lacks proper authorization checks and input validation

What is CVE-2026-28431?

CVE-2026-28431 is a critical missing authorization vulnerability in misskey-dev misskey, published on 9 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-285

Which versions are affected by CVE-2026-28431?

It affects 1 product.

Products include Misskey Misskey.

How do I fix CVE-2026-28431?

No fix has been published for CVE-2026-28431 yet. Limit exposure of the affected software until one is available.

Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.

Is CVE-2026-28431 being exploited?

There is no known exploitation of CVE-2026-28431 in the wild and no public exploit code.

Other vulnerabilities in misskey-dev misskey

• CVE-2025-25306 Misskey's Incomplete Patch of CVE-2024-52591 Leads to Forgery of Federated Notes Critical 9.3
• CVE-2023-49079 Misskey's missing signature validation allows arbitrary users to impersonate any remote user. Critical 9.3
• CVE-2023-52139 Misskey vulnerable to improper authorization when accessing with third-party application Critical 9.1
• CVE-2024-52590 Missing validation allows spoofed profiles in Misskey High 8.8
• CVE-2024-52591 Missing validation allows spoofed profiles and notes in Misskey High 8.8

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-r33c-qg3g-v9cr.