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Description

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.

PUBLISHED Reserved 2026-05-04 | Published 2026-05-12 | Updated 2026-05-13 | Assigner GitHub_M




HIGH: 7.3CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N

Problem types

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

CWE-116: Improper Encoding or Escaping of Output

Product status

>= 4.0.0-beta.1, < 4.0.5
affected

< 3.2.12
affected

References

github.com/...YAFNET/security/advisories/GHSA-8rq5-wwpp-fmj2 exploit

github.com/...YAFNET/security/advisories/GHSA-8rq5-wwpp-fmj2

cve.org (CVE-2026-43939)

nvd.nist.gov (CVE-2026-43939)

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