Vulnerability in Misskey-Dev Misskey

CVE-2026-47746

Misskey is an open source, federated social media platform. Versions 12.37.0 and later, but prior to 2026.5.4, are vulnerable to timing attacks during JSON-LD signature validation and the compaction process. Because the JSON-LD parsing context is not shared between signature verification and subsequent processing, the application may trust information that should not be trusted, resulting in a time-of-check to time-of-use (TOCTOU) flaw. This allows an attacker to have fraudulent activities accepted as valid, leading to a loss of integrity. This issue has been fixed in version 2026.5.4.

Vulnerability class: TOCTOU (Time-of-Check to Time-of-Use)

EPSS: 0.002 (8.1th percentile) — read the EPSS interpretation.