Multiple high-severity vulnerabilities in Microsoft Defender, including heap buffer overflows and TOCTOU race conditions (CVE-2026-55011, CVSS 7.8; CVE-2026-55012, CVSS 7.8), could allow an attacker to execute arbitrary code with system privileges by tricking a user into opening a malicious file. Microsoft has released updates to remediate these flaws; affected users should apply the available patches immediately via the Microsoft Security Response Center. Specific affected and fixed version numbers for Microsoft Defender for Endpoint for Mac and the Microsoft Malware Protection Engine are not detailed in this advisory.
Security Advisories Download Security Advisory; NCSC-2026-0236 [1.0.0] Security Advisory NCSC-2026-0236 [1.0.0] Publicatie 14-07-2026 20:38 (Europe/Amsterdam) Prioriteit Normaal Betreft Kwetsbaarheden verholpen in Microsoft Defender Kenmerken Heap-based Buffer Overflow Integer Overflow or Wraparound Integer Underflow (Wrap or Wraparound) Exposure of Private Personal Information to an Unauthorized Actor Time-of-check Time-of-use (TOCTOU) Race Condition Omschrijving Microsoft heeft kwetsbaarheden verholpen in Defender. Een kwaadwillende kan de kwetsbaarheden misbruiken om zich verhoogde rechten toe te kennen, willekeurige code uit te voeren met rechten van het systeem en/of toegang te krijgen tot gevoelige gegevens. De kwaadwillende moet het slachtoffer misleiden een malafide bestand te downloaden en openen. Oplossingen Microsoft heeft updates beschikbaar gesteld waarmee de beschreven kwetsbaarheden worden verholpen. We raden u aan om deze updates te installeren. Meer informatie over de kwetsbaarheden, de installatie van de updates en eventuele work-arounds vindt u op: https://portal.msrc.microsoft.com/en-us/security-guidance CVE's CVE-2026-55011 - CVSS (v3) 7.8 CVE-2026-55012 - CVSS (v3) 7.8 CVE-2026-50657 - CVSS (v3) 4.7 CVE-2026-50658 - CVSS (v3) 7.0 CVE-2026-56178 - CVSS (v3) 5.5 Producten Microsoft Microsoft Defender for Endpoint for Mac Microsoft Malware Protection Engine 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.