A 9.1 JWT signature bypass let anyone impersonate any user of the Mnemosyne agent memory sync server

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GHSA-xcw4-53cc-hv32, published 2026-09-18, covers mnemosyne-memory up to and including v3.10.0: the sync server base64-decoded JWT bearer tokens and then called a jwt library with options that disabled signature verification, so any well-formed token was accepted, including alg:none. An unauthenticated attacker with network reach could forge a token for any user_id and read or modify that user's stored agent memory. The v3.10.1 fix replaces the decode with a stdlib HS256 verifier using hmac.compare_digest, a strict alg check and UTC-aware exp validation.