Auth bypass in Misskey

CVE-2026-28431

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.

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.004 (34.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 34th percentile — 34.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-28431: held from 0.002 to 0.004.

EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-28431?
CVE-2026-28431 is a high-severity vulnerability in Misskey, classified under Improper Authorization. CVSS score: 7.5/10. Published 2026-03-10.
How severe is CVE-2026-28431?
High severity. CVSS v3 base score is 7.5 out of 10.