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

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Summary

CVECVE-2026-43939
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-12 15:16:15 UTC
Updated2026-05-12 15:16:15 UTC
DescriptionYetAnotherForum.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.

Risk And Classification

Primary CVSS: v3.1 7.3 HIGH from [email protected]

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

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

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.3HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N
3.1CNADECLARED7.3HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA YAFNET YAFNET affected >= 4.0.0-beta.1, < 4.0.5 Not specified
CNA YAFNET YAFNET affected < 3.2.12 Not specified

References

ReferenceSourceLinkTags
github.com/YAFNET/YAFNET/security/advisories/GHSA-8rq5-wwpp-fmj2 [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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