What is CVE-2026-28433?

CVE-2026-28433 is a medium-severity vulnerability in Misskey, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 4.3/10. Published 2026-03-10.

How severe is CVE-2026-28433?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Auth bypass in Misskey

CVE-2026-28433

Misskey is an open source, federated social media platform. All Misskey servers running versions 10.93.0 and later, but prior to 2026.3.1, contain a vulnerability that allows importing other users' data due to lack of ownership validation. The impact of this vulnerability is estimated to be relatively low, as bad actors would require the ID corresponding to the target file for import. This vulnerability is fixed in 2026.3.1.

Vulnerability class: IDOR (Insecure Direct Object Reference)

Published 2026-03-10 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.003 (17.4th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 17th percentile — 17.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.000

Affected products

Misskey
Misskey-Dev Misskey — versions >= 10.93.0, < 2026.3.1

Weakness classification (CWE)

References

github.com/misskey-dev/misskey/security/advisories/GHSA-g6hj-33h7-6fq8 (Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-28433?: CVE-2026-28433 is a medium-severity vulnerability in Misskey, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 4.3/10. Published 2026-03-10.
How severe is CVE-2026-28433?: Medium severity. CVSS v3 base score is 4.3 out of 10.