PYSEC-2026-4106 Mnemosyne has JWT signature verification bypass sync server that allows authentication bypass

Summary The Mnemosyne sync server's authentication check decoded JWT bearer tokens but never verified their HMAC-SHA256 signatures. Any well-formed token was accepted, allowing an unauthenticated attacker to impersonate any user and read or modify their sync data. Severity: Critical CVSS 3.1:...