High severity · published Mar 9, 2026
CVE-2026-28431
Misskey lacks proper authorization checks and input validation
7.5
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 18% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MI
misskey · misskey-dev
>= 8.45.0, < 2026.3.1 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-28431
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-28431
Vendor Advisory
https://github.com/misskey-dev/misskey/security/advisories/GHSA-r33c-qg3g-v9cr
More from misskey
9.3
CVE-2024-52591
Missing validation allows spoofed profiles and notes in Misskey
9.2
CVE-2026-46713
Misskey: JSON-LD signature validation + compaction may lead to improper activity handling
8.9
CVE-2026-47746
Misskey: JSON-LD signature validation + compaction is vulnerable to timing attacks
8.7
CVE-2026-103937
Misskey: Denial of service resulting from insufficient cleanup processing during file uploads
8.7
CVE-2026-104817
Misskey: Lack of rate limiting and size restrictions in RSS fetching API