What is CVE-2026-43939?

CVE-2026-43939 is a high-severity vulnerability in Yafnet, classified under Cross-site Scripting. CVSS score: 7.3/10. Published 2026-05-12.

How severe is CVE-2026-43939?

High severity. CVSS v3 base score is 7.3 out of 10.

XSS in Yafnet

CVE-2026-43939

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 pag…

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.000 (10.0th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N.

Affected products

Yafnet — versions >= 4.0.0-beta.1, < 4.0.5, < 3.2.12

Weakness classification (CWE)

CWE-79 — 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

References

security-advisories@github.com (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-43939?: CVE-2026-43939 is a high-severity vulnerability in Yafnet, classified under Cross-site Scripting. CVSS score: 7.3/10. Published 2026-05-12.
How severe is CVE-2026-43939?: High severity. CVSS v3 base score is 7.3 out of 10.