CVE-2025-26621: Citeum Opencti

Medium severity, CVSS 6.8. EPSS: 0.4% chance of exploitation in the next 30 days.

OpenCTI is an open source platform for managing cyber threat intelligence knowledge and observables. Prior to version 6.5.2, any user with the capability manage customizations can edit webhook that will execute javascript code. This can be abused to cause a denial of service attack by prototype pollution, making the node js server running the OpenCTI frontend become unavailable. Version 6.5.2 fixes the issue.

Affected products

• Citeum Opencti: before 6.5.2 (fixed in 6.5.2)

Published 2025-05-19. Last modified 2026-06-17.