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CVE-2026-43938

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CVE-2026-43938

Published: May 12, 2026

Modified: May 12, 2026

PUBLISHED

CVSS v3.1

8.1

HIGH

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.

VendorProductVersions

YAFNET

YAFNET

affected
>= 4.0.0-beta.1, < 4.0.5
affected
< 3.2.12

Weaknesses (CWE)

CWE-79
CWE-80
CWE-116

CVSS v3.1 Details

CVSS v3.1 Vector

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

References

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