A critical vulnerability (CVE-2026-40372, CVSS 9.1) in Microsoft ASP.NET Core involves improper verification of cryptographic signatures, allowing an authenticated attacker within a network to bypass security controls, escalate privileges, and gain unauthorized elevated access. Microsoft has released an update to remediate this issue.
Beveiligingsadviezen Download Beveilingsadvies; NCSC-2026-0123 [1.0.0] Beveiligingsadvies NCSC-2026-0123 [1.0.0] Publicatie 22-04-2026 11:40 (Europe/Amsterdam) Prioriteit Normaal Betreft Kwetsbaarheid verholpen in ASP.NET Core van Microsoft Kenmerken Improper Verification of Cryptographic Signature Omschrijving Microsoft heeft een kwetsbaarheid verholpen in ASP.NET Core. De kwetsbaarheid ontstaat door onjuiste verificatie van cryptografische handtekeningen binnen ASP.NET Core. Hierdoor kan een onbevoegde aanvaller binnen een netwerk privileges verhogen door beveiligingscontroles te omzeilen en ongeautoriseerde toegang met verhoogde rechten te verkrijgen. Oplossingen Microsoft heeft een update uitgebracht om de kwetsbaarheid te verhelpen. Zie bijgevoegde referenties voor meer informatie. Referenties https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40372 CVE's CVE-2026-40372 - CVSS (v3) 9.1 Producten Microsoft ASP.NET Core 10.0 Disclaimer The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this page to enhance access to its information and security advisories. The use of this security advisory is subject to the following terms and conditions: NCSC-NL makes every reasonable effort to ensure that the content of this page is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or continuous keeping up-to-date. The information contained in this security advisory is intended solely for the purpose of providing general information to professional users. No rights can be derived from the information provided therein. NCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of this security advisory. This includes damage resulting from the inaccuracy of incompleteness of the information contained in the advisory. This security advisory is subject to Dutch law. All disputes related to or arising from the use of this advisory will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings.