CVE-2026-43939

HIGH

YAF.NET: Stored XSS in Forum Thread Posts/Replies Allowing Arbitrary JavaScript Execution for All Thread Viewers

Title source: cna
STIX 2.1

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.

References (1)

Core 1
Core References

Scores

CVSS v3 7.3
EPSS 0.0003
EPSS Percentile 9.9%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N

CISA SSVC

Vulnrichment
Exploitation poc
Automatable no
Technical Impact total

Details

CWE
CWE-116 CWE-79 CWE-80
Status published
Products (4)
nuget/YAFNET.Core 0 - 3.2.12NuGet
nuget/YAFNET.Core 4.0.0-beta01 - 4.0.5NuGet
YAFNET/YAFNET < 3.2.12
YAFNET/YAFNET >= 4.0.0-beta.1, < 4.0.5
Published May 12, 2026
Tracked Since May 12, 2026