CVE-2026-43939
CVE-2026-43939 is a high-severity vulnerability with a CVSS 3.x base score of 7.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.
Key facts
- Severity: High (CVSS 3.x base score 7.3)
- EPSS exploit prediction: 0% (10th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-29481
- Weakness: CWE-79
- Published:
- Last modified:
Description
YetAnotherForum.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.
Frequently asked questions
- What is CVE-2026-43939?
- YetAnotherForum.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.
- How severe is CVE-2026-43939?
- CVE-2026-43939 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
- Is CVE-2026-43939 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (10th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-43939?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2026-43939 have an EU (EUVD) identifier?
- Yes. CVE-2026-43939 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29481.
- When was CVE-2026-43939 published?
- CVE-2026-43939 was published on 2026-05-12 and last updated on 2026-06-17.
References
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