{"api_version":"1","generated_at":"2026-05-12T20:58:18+00:00","cve":"CVE-2026-43938","urls":{"html":"https://cve.report/CVE-2026-43938","api":"https://cve.report/api/cve/CVE-2026-43938.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-43938","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-43938"},"summary":{"title":"YAF.NET: Unauthenticated Stored Second-Order XSS in Admin Event Log via Reflected `User-Agent` Header","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.","state":"PUBLISHED","assigner":"GitHub_M","published_at":"2026-05-12 15:16:15","updated_at":"2026-05-12 16:16:24"},"problem_types":["CWE-79","CWE-80","CWE-116","CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","CWE-80 CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)","CWE-116 CWE-116: Improper Encoding or Escaping of Output"],"metrics":[{"version":"3.1","source":"security-advisories@github.com","type":"Secondary","score":"8.1","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","data":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","baseScore":8.1,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"NONE"}},{"version":"3.1","source":"CNA","type":"DECLARED","score":"8.1","severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","data":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":8.1,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","version":"3.1"}}],"references":[{"url":"https://github.com/YAFNET/YAFNET/security/advisories/GHSA-33gv-fc78-qgf5","name":"https://github.com/YAFNET/YAFNET/security/advisories/GHSA-33gv-fc78-qgf5","refsource":"134c704f-9b21-4f2e-91b3-4a467353bcc0","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-43938","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43938","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"YAFNET","product":"YAFNET","version":"affected >= 4.0.0-beta.1, < 4.0.5","platforms":[]},{"source":"CNA","vendor":"YAFNET","product":"YAFNET","version":"affected < 3.2.12","platforms":[]}],"timeline":[],"solutions":[],"workarounds":[],"exploits":[],"credits":[],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"adp":[{"metrics":[{"other":{"content":{"id":"CVE-2026-43938","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"total"}],"role":"CISA Coordinator","timestamp":"2026-05-12T15:39:17.598324Z","version":"2.0.3"},"type":"ssvc"}}],"providerMetadata":{"dateUpdated":"2026-05-12T15:39:46.446Z","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP"},"references":[{"tags":["exploit"],"url":"https://github.com/YAFNET/YAFNET/security/advisories/GHSA-33gv-fc78-qgf5"}],"title":"CISA ADP Vulnrichment"}],"cna":{"affected":[{"product":"YAFNET","vendor":"YAFNET","versions":[{"status":"affected","version":">= 4.0.0-beta.1, < 4.0.5"},{"status":"affected","version":"< 3.2.12"}]}],"descriptions":[{"lang":"en","value":"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."}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":8.1,"baseSeverity":"HIGH","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-79","description":"CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-80","description":"CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)","lang":"en","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-116","description":"CWE-116: Improper Encoding or Escaping of Output","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-05-12T13:57:56.951Z","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M"},"references":[{"name":"https://github.com/YAFNET/YAFNET/security/advisories/GHSA-33gv-fc78-qgf5","tags":["x_refsource_CONFIRM"],"url":"https://github.com/YAFNET/YAFNET/security/advisories/GHSA-33gv-fc78-qgf5"}],"source":{"advisory":"GHSA-33gv-fc78-qgf5","discovery":"UNKNOWN"},"title":"YAF.NET: Unauthenticated Stored Second-Order XSS in Admin Event Log via Reflected `User-Agent` Header"}},"cveMetadata":{"assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","assignerShortName":"GitHub_M","cveId":"CVE-2026-43938","datePublished":"2026-05-12T13:57:56.951Z","dateReserved":"2026-05-04T16:59:09.089Z","dateUpdated":"2026-05-12T15:39:46.446Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-05-12 15:16:15","lastModifiedDate":"2026-05-12 16:16:24","problem_types":["CWE-79","CWE-80","CWE-116","CWE-79 CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","CWE-80 CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)","CWE-116 CWE-116: Improper Encoding or Escaping of Output"],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","baseScore":8.1,"baseSeverity":"HIGH","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"REQUIRED","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"HIGH","availabilityImpact":"NONE"},"exploitabilityScore":2.8,"impactScore":5.2}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"43938","Ordinal":"1","Title":"YAF.NET: Unauthenticated Stored Second-Order XSS in Admin Event ","CVE":"CVE-2026-43938","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"43938","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"YAF.NET: Unauthenticated Stored Second-Order XSS in Admin Event "}]}}}