Microsoft has disclosed CVE-2026-56178, an elevation-of-privilege flaw in Microsoft Defender for Endpoint on macOS, affecting agent builds earlier than 101.26042.0020. The fix is already available in the June 2026 release, and organizations should treat the advisory as a prompt to verify that their managed Macs have actually received it.
Microsoft’s Security Update Guide published the CVE on July 14, 2026. The National Vulnerability Database records the issue as a time-of-check/time-of-use (TOCTOU) race condition, assigned CWE-367, that can allow an authorized local attacker to elevate privileges. Microsoft rated it 5.5 out of 10 under CVSS 3.1, with a vector requiring local access and low privileges but no user interaction.
For Windows-focused IT teams, this is a cross-platform reminder with a familiar lesson: Defender for Endpoint is not just a cloud service or a Windows component. Its macOS agent runs locally, integrates with Apple’s system-extension architecture, and must be patched on the same disciplined cadence as Windows Defender platform updates.
The critical version number is 101.26042.0020. According to Microsoft’s advisory data published through the NVD, Microsoft Defender for Endpoint for Mac versions from 101.0.0 up to, but not including, 101.26042.0020 are affected.
Microsoft’s Defender for Endpoint release notes list build 101.26042.0020 as the June 2026 macOS release, carrying application version 20.126042.20.0, engine version 1.1.26040.3000, and security intelligence version 1.453.151.0. The notes describe that package broadly as containing “security and critical updates,” without naming CVE-2026-56178 directly.
That release has now been superseded by the July 2026 build, 101.26052.0016, with application version 20.126052.16.0. For administrators, the practical target should not be the minimum fixed build unless there is a tightly controlled compatibility reason to stop there. Deploy the current production release and verify the installed version across the fleet.
This chronology also matters. The public advisory appeared on July 14, but the minimum fixed version was released in June. That suggests Microsoft shipped the remediation before publicly documenting the defect, a common but important distinction when assessing exposure windows and patch compliance.
The affected condition is a race between a security check and a later use of the object that was checked. In a TOCTOU vulnerability, code validates a file, path, permission, or other resource at one moment, then assumes it remains unchanged when it performs a privileged operation. If an attacker can swap or alter that resource in the interval, the privileged component can be induced to act on something other than the item it originally verified.
Microsoft has not published root-cause details, proof-of-concept code, or the exact Defender component involved. That absence is worth respecting. It would be premature to claim that the flaw compromises real-time protection, bypasses macOS System Integrity Protection, or grants root in every deployment. The confirmed scope is narrower: an authorized attacker can exploit a local race condition in the Defender for Endpoint Mac agent to elevate privileges.
CISA’s Stakeholder-Specific Vulnerability Categorization entry currently records exploitation as “none,” automation as “no,” and technical impact as “partial.” That does not mean the vulnerability is harmless, nor does it guarantee the lack of exploitation will persist. It means there is presently no public indication of active exploitation or an easily automated mass-attack path.
That risk profile is also why a medium CVSS score should not lead to a routine monthly deferral. A local attacker who already has an initial foothold often wants precisely this next step: move from a restricted user context to a more powerful one, disable controls, access protected material, or establish more durable persistence.
For a mixed Windows and Mac estate, the likely weak point is process rather than technical complexity. Windows Defender platform updates are often monitored through Microsoft Update, Configuration Manager, Intune reporting, or endpoint-management dashboards. Defender for Endpoint on macOS uses Microsoft AutoUpdate, and the agent’s update behavior may be governed by configuration profiles and separate release-ring choices.
Microsoft’s macOS update documentation says Microsoft AutoUpdate periodically downloads and installs Defender for Endpoint updates by default. But “periodically” is not a sufficient security control when devices are offline, user-owned, held behind restrictive egress policies, or assigned to a preview channel that has drifted from the organization’s desired baseline.
On an individual Mac, Microsoft documents the following command for checking the installed Defender application version:
Microsoft’s own release notes use platform build numbers such as 101.26042.0020, while the local health command may return the corresponding application version, such as 20.126042.20.0. Administrators should account for that naming difference in compliance queries and deployment reporting rather than treating it as a version mismatch.
Microsoft also provides
That command is useful for validation systems, break-glass remediation, and devices that did not pick up the package through their management workflow. In an enterprise, however, the durable response is to refresh the Defender package in Intune, Jamf Pro, or the organization’s chosen macOS management platform, then use deployment reporting to confirm installation and post-update health.
Microsoft notes that Defender for Endpoint on macOS versions expire after six months, even though expired agents can continue receiving security intelligence updates. That policy creates an easy trap: a Mac can appear protected because definitions still update, while the underlying agent misses fixes such as this one. Check the expiry status as well:
The appropriate response is straightforward: move every managed Mac to 101.26042.0020 or later, preferably July’s 101.26052.0016 release, and make sure the asset inventory can prove it. The next risk is not the race condition itself; it is discovering that “automatic updates” left a pocket of Macs on an older Defender build.
Microsoft’s Security Update Guide published the CVE on July 14, 2026. The National Vulnerability Database records the issue as a time-of-check/time-of-use (TOCTOU) race condition, assigned CWE-367, that can allow an authorized local attacker to elevate privileges. Microsoft rated it 5.5 out of 10 under CVSS 3.1, with a vector requiring local access and low privileges but no user interaction.
For Windows-focused IT teams, this is a cross-platform reminder with a familiar lesson: Defender for Endpoint is not just a cloud service or a Windows component. Its macOS agent runs locally, integrates with Apple’s system-extension architecture, and must be patched on the same disciplined cadence as Windows Defender platform updates.
The Patch Line Is 101.26042.0020
The critical version number is 101.26042.0020. According to Microsoft’s advisory data published through the NVD, Microsoft Defender for Endpoint for Mac versions from 101.0.0 up to, but not including, 101.26042.0020 are affected.Microsoft’s Defender for Endpoint release notes list build 101.26042.0020 as the June 2026 macOS release, carrying application version 20.126042.20.0, engine version 1.1.26040.3000, and security intelligence version 1.453.151.0. The notes describe that package broadly as containing “security and critical updates,” without naming CVE-2026-56178 directly.
That release has now been superseded by the July 2026 build, 101.26052.0016, with application version 20.126052.16.0. For administrators, the practical target should not be the minimum fixed build unless there is a tightly controlled compatibility reason to stop there. Deploy the current production release and verify the installed version across the fleet.
This chronology also matters. The public advisory appeared on July 14, but the minimum fixed version was released in June. That suggests Microsoft shipped the remediation before publicly documenting the defect, a common but important distinction when assessing exposure windows and patch compliance.
A Local Privilege Escalation, Not a Remote Defender Break-In
The CVSS vector tells the operational story more clearly than the generic “elevation of privilege” label. An attacker needs local access to an affected Mac and must already hold low-level privileges. There is no network attack path and no requirement for a victim to click through a prompt.The affected condition is a race between a security check and a later use of the object that was checked. In a TOCTOU vulnerability, code validates a file, path, permission, or other resource at one moment, then assumes it remains unchanged when it performs a privileged operation. If an attacker can swap or alter that resource in the interval, the privileged component can be induced to act on something other than the item it originally verified.
Microsoft has not published root-cause details, proof-of-concept code, or the exact Defender component involved. That absence is worth respecting. It would be premature to claim that the flaw compromises real-time protection, bypasses macOS System Integrity Protection, or grants root in every deployment. The confirmed scope is narrower: an authorized attacker can exploit a local race condition in the Defender for Endpoint Mac agent to elevate privileges.
CISA’s Stakeholder-Specific Vulnerability Categorization entry currently records exploitation as “none,” automation as “no,” and technical impact as “partial.” That does not mean the vulnerability is harmless, nor does it guarantee the lack of exploitation will persist. It means there is presently no public indication of active exploitation or an easily automated mass-attack path.
Why Defender Agents Deserve Their Own Patch SLA
Endpoint security agents occupy a sensitive position. They inspect files, observe processes, integrate with operating-system security subsystems, and commonly run components with permissions beyond those given to ordinary applications. A defect in that boundary is especially unwelcome because the product installed to reduce endpoint risk can become a local privilege-escalation opportunity.That risk profile is also why a medium CVSS score should not lead to a routine monthly deferral. A local attacker who already has an initial foothold often wants precisely this next step: move from a restricted user context to a more powerful one, disable controls, access protected material, or establish more durable persistence.
For a mixed Windows and Mac estate, the likely weak point is process rather than technical complexity. Windows Defender platform updates are often monitored through Microsoft Update, Configuration Manager, Intune reporting, or endpoint-management dashboards. Defender for Endpoint on macOS uses Microsoft AutoUpdate, and the agent’s update behavior may be governed by configuration profiles and separate release-ring choices.
Microsoft’s macOS update documentation says Microsoft AutoUpdate periodically downloads and installs Defender for Endpoint updates by default. But “periodically” is not a sufficient security control when devices are offline, user-owned, held behind restrictive egress policies, or assigned to a preview channel that has drifted from the organization’s desired baseline.
Verify the Fleet Rather Than Trusting the Console Summary
Admins should inventory every macOS device running Microsoft Defender for Endpoint, then identify systems below build 101.26042.0020. Do not confuse antivirus intelligence updates with agent updates: current signatures do not establish that the vulnerable application code has been replaced.On an individual Mac, Microsoft documents the following command for checking the installed Defender application version:
mdatp health --field app_versionMicrosoft’s own release notes use platform build numbers such as 101.26042.0020, while the local health command may return the corresponding application version, such as 20.126042.20.0. Administrators should account for that naming difference in compliance queries and deployment reporting rather than treating it as a version mismatch.
Microsoft also provides
msupdate for administrators that need to force an update rather than waiting for the normal AutoUpdate cycle:
Code:
cd /Library/Application\ Support/Microsoft/MAU2.0/Microsoft\ AutoUpdate.app/Contents/MacOS
./msupdate --install --apps wdav00Microsoft notes that Defender for Endpoint on macOS versions expire after six months, even though expired agents can continue receiving security intelligence updates. That policy creates an easy trap: a Mac can appear protected because definitions still update, while the underlying agent misses fixes such as this one. Check the expiry status as well:
mdatp health --field product_expirationThe Real Deadline Is the Next Compliance Report
CVE-2026-56178 is not currently documented as an in-the-wild attack, and its local, low-privilege prerequisite limits immediate opportunistic exposure. Still, the remediation is already in the production update stream, the fixed threshold is clear, and the affected product is a privileged endpoint agent.The appropriate response is straightforward: move every managed Mac to 101.26042.0020 or later, preferably July’s 101.26052.0016 release, and make sure the asset inventory can prove it. The next risk is not the race condition itself; it is discovering that “automatic updates” left a pocket of Macs on an older Defender build.
References
- Primary source: MSRC
Published: 2026-07-14T07:00:00-07:00
Security Update Guide - Microsoft Security Response Center
msrc.microsoft.com
- Official source: learn.microsoft.com
Microsoft Defender for Endpoint release notes - Microsoft Defender for Endpoint | Microsoft Learn
This article describes releases of Microsoft Defender for Endpoint on Windows, macOS, Linux, Android, and iOS.learn.microsoft.com - Related coverage: advdownload.advantech.com
- Related coverage: techradar.com
Microsoft says it's hard at work on a patch for this worrying Defender zero-day | TechRadar
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