{"id":"CVE-2026-43938","summary":"YAF.NET: Unauthenticated Stored Second-Order XSS in Admin Event Log via Reflected `User-Agent` Header","details":"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.","aliases":["GHSA-33gv-fc78-qgf5"],"modified":"2026-07-08T08:05:14.276678839Z","published":"2026-05-12T13:57:56.951Z","database_specific":{"cwe_ids":["CWE-116","CWE-79","CWE-80"],"cna_assigner":"GitHub_M","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43938.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43938.json"},{"type":"ADVISORY","url":"https://github.com/YAFNET/YAFNET/security/advisories/GHSA-33gv-fc78-qgf5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43938"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/yafnet/yafnet","events":[{"introduced":"c2932f06fe41f11e723879f8febf3e96b91d5750"},{"fixed":"3cb0ee7fbc01f8d3e84eaddf55350aced2dd4bfc"},{"introduced":"0"},{"fixed":"28579da80af507294dbdf9ae5b44ad9c185d0720"}],"database_specific":{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"4.0.0-beta.1"},{"fixed":"4.0.5"},{"introduced":"0"},{"fixed":"3.2.12"}]}}],"versions":["v3.2.11","v4.0.4","v4.0.3","v4.0.2","v3.2.10","v3.2.9","v4.0.1","v3.2.8","v4.0.0","v4.0.0-rc.4","v3.2.7","v3.2.6","v4.0.0-rc.3","v4.0.0-rc.2","v4.0.0-rc.1","v3.2.5","v3.2.4","v4.0.0-beta.7","v3.2.3","v4.0.0-beta.3","v4.0.0-beta.1","v3.2.2","v3.2.1","v3.2.0","v3.1.15","v3.1.14","v3.1.13","v3.1.12","v3.1.11","v3.1.10","v3.1.9","v3.1.8","v3.1.7","v3.1.6","v3.1.5","v3.1.4","v3.1.3","v3.1.2","v3.1.1","v3.1.0","v3.0.2","v2.3.1.0","v2.3.0.5-beta.1","v2.3.0.4","v2.3.0.4-beta.1","v2.3.0.0","v2.3.0.0-rc.5","v2.3.0.0-rc.4","v2.3.0.0-rc.3","v2.3.0.0-rc.2","v2.3.0.0-rc.1","v2.3.0.0-beta.4","v2.3.0.0-beta.3","v2.3.0.0-beta.2","v2.3.0.0-BETA1","v2.2.4.19","v2.2.4.18","v2.2.4.10","v2.2.4.9","v2.2.4.8","v2.2.4.7","v2.2.4.6","v2.2.4.5","v2.2.4.4","v2.2.4.3","v2.2.4.2","v2.2.4.1","v2.2.4.0","v2.2.4.0-nightly","v2.2.3","v2.2.3.0-nightly.118","v2.2.3.0-nightly.115","v2.2.2","v2.2.2.0-nightly.76","v2.2.1","v2.2.1.0-nightly.20","v2.2.0","v2.2.0-rc.1","v2.2.0-beta.1","v2.1.2-beta.1","v2.1.2","v2.1","v2.0.0","release_2_0_0_RC1","release_1_9_6_1_RTW","release_1_9_6_FINAL","release_1_9_6_RC1","release_1_9_6_BETA1","release_1_9_5_5_RTW","release_1_9_5_5_BETA","release_1_9_5_RC1","release_1_9_4_FINAL","release_1_9_4_BETA","release_1_0_2","aspnet20a","complete2","complete","release_0_9_9b","release_0_9_9","yaf_dnn2","release_0_9_8B","release_0_9_8","release_0_9_7","release_0_9_6","release_0_9_5","release_0_9_4","release_0_9_3","release_0_9_2","release_0_9_1","release_0_9_0","release_0_8_2","release_0_8_1","start"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43938.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N"}]}