CVE-2026-28431
Critical data exposure on Misskey servers via poor access checks.
Is CVE-2026-28431 being exploited?
Not confirmed. CVE-2026-28431 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.25% probability of exploitation in the next 30 days.
How severe is CVE-2026-28431?
CVE-2026-28431 is rated Critical with a CVSS score of 9.2. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-28431?
Yes. A fix has been recorded for CVE-2026-28431. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-28431 affect?
CVE-2026-28431 affects Misskey 8.45.0 - 2026.3.0. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-28431?
Upgrade to 2026.3.1+; validate permissions.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Unauthorized data access on Misskey servers due to weak permission checks and input validation; risk of data breach.
Immediate action required
- affected>= 8.45.0 and < 2026.3.1
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.