---
id: "CVE-2026-121938"
kind: "vulnerability"
aliases: ["CVE-2026-121938"]
title: "langchain4j-aideepin: any logged-in user can read others' character chats"
severity: "medium"
cvss: 6.0
epss: null
exploited: false
status: "open"
category: "ai-tooling"
products: []
ecosystems: []
tags: ["ai-tooling", "java", "langchain4j-aideepin", "multi-user", "self-hosted"]
not_affected_if: ["single-user", "version-3.31.0-or-later"]
published_at: "2026-11-04T13:17:28+00:00"
first_seen_at: "2026-11-04T13:27:02+00:00"
updated_at: "2026-11-04T13:28:11+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121938", "first_seen_at": "2026-11-04T13:27:02+00:00"}]
---

# langchain4j-aideepin: any logged-in user can read others' character chats

langchain4j-aideepin before 3.31.0 has an insecure direct object reference: GET /character/{uuid} returns a character's data without checking that the requester owns it. An authenticated user who knows another user's character uuid can read that person's questions, AI answers, and attachment and audio URLs.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the langchain4j-aideepin version in use; affected builds are those before `3.31.0`.
- Look for the `CharacterService.detail` lookup behind `GET /character/{uuid}` and confirm whether it verifies the caller owns the character.

## Fix

- langchain4j-aideepin: move to `3.31.0` or later.

## Timeline

- 2026-11-04T13:27:02+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-121938

## Documents

- [advisory] Third-party advisory: www.vulncheck.com https://www.vulncheck.com/advisories/langchain4j-aideepin-before-3.31.0-idor-via-get-character-uuid
- [fix] Patch: github.com https://github.com/moyangzhan/langchain4j-aideepin/commit/9b2fee6b66836a0efd5599cfcddd05b80b05ca93

## From the sources

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.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_