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

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/moyangzhan/langchain4j-aideepin/pull/117
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/moyangzhan/langchain4j-aideepin/commit/9b2fee6b66836a0efd5599cfcddd05b80b05ca93

## Affected products and versions

- moyangzhan / langchain4j-aideepin (moyangzhan/langchain4j-aideepin): ≥ 0; < 3.31.0 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6 (medium); 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; source: CNA: VulnCheck

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-639

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/moyangzhan/langchain4j-aideepin/issues/116 (CNA: VulnCheck; issue-tracking)

- https://hackmd.io/@hieuPenguinnn/langchain4j-aideepin-character-conversation-cross-user-idor (CNA: VulnCheck; third-party-advisory)

- https://github.com/moyangzhan/langchain4j-aideepin/pull/117 (CNA: VulnCheck; issue-tracking, patch)

- https://github.com/moyangzhan/langchain4j-aideepin/commit/9b2fee6b66836a0efd5599cfcddd05b80b05ca93 (CNA: VulnCheck; patch)

- https://github.com/moyangzhan/langchain4j-aideepin/blob/v3.30.0/server/adi-common/src/main/java/com/moyz/adi/common/service/CharacterService.java#L105-L125 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/langchain4j-aideepin-before-3.31.0-idor-via-get-character-uuid (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121938; retrieved 2026-11-04; source updated 2026-11-04

Revision: 24f283848b4a8fa442bd60dc5d2486d2b29fbef2ebc09a433d2113ba579f16d5

Canonical: https://y2.dev/cve/CVE-2026-121938

## Agent and API access

Public CVE pages, Markdown, and JSON are free to read without an account or API key.

- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search, filters, sort, and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.