{
"document": {
"acknowledgments": [
{
"names": [
" Damir Moldovanov "
]
},
{
"names": [
"ACD421 with Hollow Point Labs"
]
},
{
"names": [
"ACD421 with Hollow Point Labs"
]
},
{
"names": [
"Anonymous"
]
},
{
"names": [
"Diffract"
]
},
{
"names": [
"Sibusiso with Ironsky"
]
}
],
"aggregate_severity": {
"namespace": "https://www.microsoft.com/en-us/msrc/security-update-severity-rating-system",
"text": "Important"
},
"category": "csaf_security_advisory",
"csaf_version": "2.0",
"distribution": {
"text": "Public",
"tlp": {
"label": "WHITE",
"url": "https://www.first.org/tlp/"
}
},
"lang": "en-US",
"notes": [
{
"category": "general",
"text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
"title": "Additional Resources"
},
{
"category": "legal_disclaimer",
"text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
"title": "Disclaimer"
},
{
"category": "general",
"text": "Required. The vulnerability documented by this CVE requires customer action to resolve.",
"title": "Customer Action"
}
],
"publisher": {
"category": "vendor",
"contact_details": "secure@microsoft.com",
"name": "Microsoft Security Response Center",
"namespace": "https://msrc.microsoft.com"
},
"references": [
{
"category": "self",
"summary": "CVE-2026-41091 Microsoft Defender Elevation of Privilege Vulnerability - HTML",
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-41091"
},
{
"category": "self",
"summary": "CVE-2026-41091 Microsoft Defender Elevation of Privilege Vulnerability - CSAF",
"url": "https://msrc.microsoft.com/csaf/advisories/2026/msrc_cve-2026-41091.json"
},
{
"category": "external",
"summary": "Microsoft Exploitability Index",
"url": "https://www.microsoft.com/en-us/msrc/exploitability-index?rtc=1"
},
{
"category": "external",
"summary": "Microsoft Support Lifecycle",
"url": "https://support.microsoft.com/lifecycle"
},
{
"category": "external",
"summary": "Common Vulnerability Scoring System",
"url": "https://www.first.org/cvss"
}
],
"title": "Microsoft Defender Elevation of Privilege Vulnerability",
"tracking": {
"current_release_date": "2026-05-19T07:00:00.000Z",
"generator": {
"date": "2026-05-22T22:03:01.452Z",
"engine": {
"name": "MSRC Generator",
"version": "1.0"
}
},
"id": "msrc_CVE-2026-41091",
"initial_release_date": "2026-05-12T07:00:00.000Z",
"revision_history": [
{
"date": "2026-05-19T07:00:00.000Z",
"legacy_version": "1",
"number": "1",
"summary": "Information published."
}
],
"status": "final",
"version": "1"
}
},
"vulnerabilities": [
{
"cve": "CVE-2026-41091",
"cwe": {
"id": "CWE-59",
"name": "Improper Link Resolution Before File Access ('Link Following')"
},
"notes": [
{
"category": "general",
"text": "Microsoft",
"title": "Assigning CNA"
},
{
"category": "faq",
"text": "An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.",
"title": "What privileges could be gained by an attacker who successfully exploited this vulnerability?"
},
{
"category": "faq",
"text": "Last version of the Microsoft Malware Protection Engine affected by this vulnerability: Last version of the Microsoft Malware Protection Engine affected by this vulnerability, 1.1.26030.3008: 1.1.26030.3008, First version of the Microsoft Malware Protection Engine with this vulnerability addressed: First version of the Microsoft Malware Protection Engine with this vulnerability addressed, Version 1.1.26040.8: Version 1.1.26040.8\nSee Manage Updates Baselines Microsoft Defender Antivirus for more information.\nVulnerability scanners are looking for specific binaries and version numbers on devices. Microsoft Defender files are still on disk even when disabled. Systems that have disabled Microsoft Defender are not in an exploitable state.\nIn response to a constantly changing threat landscape, Microsoft frequently updates malware definitions and the Microsoft Malware Protection Engine. In order to be effective in helping protect against new and prevalent threats, antimalware software must be kept up to date with these updates in a timely manner.\nFor enterprise deployments as well as end users, the default configuration in Microsoft antimalware software helps ensure that malware definitions and the Microsoft Malware Protection Engine are kept up to date automatically. Product documentation also recommends that products are configured for automatic updating.\nBest practices recommend that customers regularly verify whether software distribution, such as the automatic deployment of Microsoft Malware Protection Engine updates and malware definitions, is working as expected in their environment.\nMicrosoft typically releases an update for the Microsoft Malware Protection Engine once a month or as needed to protect against new threats. Microsoft also typically updates the malware definitions three times daily and can increase the frequency when needed.\nDepending on which Microsoft antimalware software is used and how it is configured, the software may search for engine and definition updates every day when connected to the Internet, up to multiple times daily. Customers can also choose to manually check for updates at any time.\nThe Microsoft Malware Protection Engine, mpengine.dll, provides the scanning, detection, and cleaning capabilities for Microsoft antivirus and antispyware software.\nDefender runs on all supported version of Windows.\nYes, Microsoft System Center Endpoint Protection, Microsoft System Center 2012 R2 Endpoint Protection, Microsoft System Center 2012 Endpoint Protection and Microsoft Security Essentials.\nYes. In addition to the changes that are listed for this vulnerability, this update includes defense-in-depth updates to help improve security-related features.",
"title": "Microsoft Defender is disabled in my environment, why are vulnerability scanners showing that I am vulnerable to this issue?"
}
],
"product_status": {
"fixed": [
"11902"
],
"known_affected": [
"1"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2026-41091 Microsoft Defender Elevation of Privilege Vulnerability - HTML",
"url": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-41091"
},
{
"category": "self",
"summary": "CVE-2026-41091 Microsoft Defender Elevation of Privilege Vulnerability - CSAF",
"url": "https://msrc.microsoft.com/csaf/advisories/2026/msrc_cve-2026-41091.json"
}
],
"scores": [
{
"cvss_v3": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"environmentalsScore": 0.0,
"exploitCodeMaturity": "UNPROVEN",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"remediationLevel": "OFFICIAL_FIX",
"reportConfidence": "CONFIRMED",
"scope": "UNCHANGED",
"temporalScore": 6.8,
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C",
"version": "3.1"
},
"products": [
"1"
]
}
],
"threats": [
{
"category": "impact",
"details": "Elevation of Privilege"
},
{
"category": "exploit_status",
"details": "Publicly Disclosed:Yes;Exploited:Yes;Latest Software Release:Exploitation Detected"
}
],
"title": "Microsoft Defender Elevation of Privilege Vulnerability"
}
]
}