CVE-2026-55011: Microsoft Defender Remote Code Execution Vulnerability
Integer underflow (wrap or wraparound) in Microsoft Defender allows an unauthorized attacker to execute code locally.
CSIRTS triage
- What
- Integer underflow (wrap or wraparound) in Microsoft Defender allows an unauthorized attacker to execute code locally.
- Who is affected
- Unauthorized users targeting systems with Microsoft Defender.
- Urgency
- Remediation is urgent due to the high severity and potential for local code execution.
- Action
- Apply the latest security patch for Microsoft Defender.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55011
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-550110.37% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 30% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-55011 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- medium[NEW] [medium] Microsoft Malware Protection Engine and Defender: Multiple vulnerabilitiescert-bund
- unknownMultiple vulnerabilities in Microsoft products (July 15, 2026)cert-fr-avis
- unknownNCSC-2026-0236 [1.00] [M/H] Vulnerabilities fixed in Microsoft Defenderncsc-nl
- highCVE-2026-55011: Integer underflow (wrap or wraparound) in Microsoft Defender allows an unauthorized attacker t…nvd
Recent advisories for Microsoft Defender Remote
A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.
- highCVE-2026-55012: Microsoft Defender Remote Code Execution Vulnerabilitymsrc · 2026-07-14
- criticalexploitedCVE-2021-1647: Microsoft Defender Remote Code Execution Vulnerabilitycisa-kev · 2021-11-03
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