CVE-2026-125386 is a security vulnerability in langchain4j-aideepin, a Java-based library for AI development, affecting versions up to 3.32.0. The flaw is an Insecure Direct Object Reference (IDOR) vulnerability in the CharacterMessageController, allowing authenticated users to access other users' message references through the knowledge-embedding-ref, memory-embedding-ref, or graph-ref endpoints by supplying a different user's message UUID. This allows attackers to obtain sensitive information such as knowledge-base chunks, long-term memory text, and knowledge-graph data. This vulnerability matters to developers and operators of AI agents using langchain4j-aideepin, as it enables unauthorized access to sensitive data, potentially compromising model performance and user trust.