CVE-2026-43939: Yafnet

High severity, CVSS 7.3. EPSS: 0.4% chance of exploitation in the next 30 days.

YetAnotherForum.NET (YAF.NET) is a C# ASP.NET forum. Prior to 4.0.5 and 3.2.12, the thread posting and reply feature accepts user-supplied content via a a post or reply that is stored server-side and later rendered back into the thread page without adequate HTML sanitization or contextual output encoding. This vulnerability is fixed in 4.0.5 and 3.2.12.

Affected products

• Yafnet Yafnet: from 4.0.0-beta.1, before 4.0.5 (fixed in 4.0.5); before 3.2.12 (fixed in 3.2.12)

Published 2026-05-12. Last modified 2026-06-17.