CVE-2026-121938: langchain4j-aideepin before 3.31.0 contains an insecure direct object reference vulnerability that allows authenticated

langchain4j-aideepin before 3.31.0 contains an insecure direct object reference vulnerability that allows authenticated users to read other users' character-chat conversations by supplying their character uuid. Attackers can request GET /character/{uuid}, which CharacterService.detail resolves without an ownership check, to obtain victims' questions, AI answers, and attachment and audio URLs.