This vulnerability involves unsafe deserialization in the AgenticScopeSerializer.fromJson function of langchain4j's LangChain4j-agentic component. It allows remote attackers to exploit deserialization if the application has enabled AgenticScope persistence and if the attacker can write to that persistence store. The flaw affects specific beta versions up to 1.5.3-beta10, 1.11.10-beta18, and 1.18.1-beta27. The vulnerability was reported privately and fixed promptly in releases dated 29 July 2026. Exploitation complexity is high, requiring specific conditions, and no known exploits are currently in the wild.

The vulnerability could allow remote attackers to perform unsafe deserialization, potentially leading to limited compromise of the affected application. However, exploitation requires the application to have enabled an opt-in feature (AgenticScope persistence) and for the attacker to have write access to the persistence store, significantly limiting the attack surface. The CVSS score of 2.1 reflects a low severity impact with high attack complexity and required privileges.

Upgrade langchain4j to versions 1.5.3-beta11, 1.11.10-beta19, or 1.18.1-beta28 or later, as these releases contain the official fix for this vulnerability. Ensure that AgenticScope persistence is only enabled when necessary and restrict write access to the persistence store to trusted entities. No additional mitigation is required beyond applying the official patches and following these configuration recommendations.