CVE-2026-43938
Description
YetAnotherForum.NET (YAF.NET) is a C# ASP.NET forum. Prior to 4.0.5 and 3.2.12, the application's database logger (YAFNET.Core/Logger/DbLogger.cs) captures the incoming request's User-Agent header into a JObject, serializes it with JsonConvert, and stores the result in the EventLog.Description column whenever an event (e.g., an unhandled exception) is logged. The admin event-log page (YetAnotherForum.NET/Pages/Admin/EventLog.cshtml.cs) later deserializes that JSON in FormatStackTrace() and interpolates the UserAgent value directly into an HTML string with no encoding, and the Razor view EventLog.cshtml emits the result through @Html.Raw. This vulnerability is fixed in 4.0.5 and 3.2.12.
How to fix
- YAFNET.Core4.0.5, 3.2.12 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| YAFNET.CoreNuGet | 4.0.0-beta01 ≤ v < 4.0.5, v < 3.2.12 | 4.0.5, 3.2.12 |
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