CVE-2021-4461: Seeyon Zhiyuan Oa Web Application System

Critical severity, CVSS 9.3. EPSS: 0.5% chance of exploitation in the next 30 days.

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.

Affected products

• Seeyon Zhiyuan Oa Web Application System: up to and including 7.0 SP1

Published 2025-10-30. Last modified 2026-06-17.