# CVE-2026-121938: langchain4j-aideepin before 3.31.0 IDOR via GET /character/{uuid}


- **Severity:** Medium 6.0 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 4 Nov 2026
- **Updated:** 4 Nov 2026
- **Also known as:** GHSA-j5gc-wvrm-78hc

## What is CVE-2026-121938?

CVE-2026-121938 is a medium-severity vulnerability in moyangzhan langchain4j-aideepin, published on 4 Nov 2026. 

### Official description

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.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-121938?


## How do I fix CVE-2026-121938?

No fix has been published for CVE-2026-121938 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-121938 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-121938 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-121938 and fix it if it is affected.

What it is: CVE-2026-121938 is a medium-severity vulnerability in moyangzhan langchain4j-aideepin, published on 4 Nov 2026. 
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-121938 exists.

Affected product: moyangzhan langchain4j-aideepin. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-121938/ (Markdown: https://insights.sbomify.com/CVE-2026-121938/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-121938
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121938
- OSV: https://osv.dev/vulnerability/CVE-2026-121938

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-121938/
Summaries are generated and may contain mistakes; the official description above is the record.