CVE-2026-50657: 
Microsoft Defender for Endpoint (ATP) vulnerability analysis and mitigation

CVE-2026-50657 is an information disclosure vulnerability in Microsoft Defender for Endpoint for macOS, classified as exposure of private personal information to an unauthorized actor (CWE-359). It allows a locally authenticated, low-privileged attacker to disclose sensitive personal information processed by the Defender agent. The vulnerability affects versions from 101.0.0 up to (excluding) 101.26042.0020 on macOS. It was published on July 14, 2026, as part of Microsoft's July 2026 Patch Tuesday release. The CVSS v3.1 base score is 5.5 (Medium) per NVD, and 4.7 (Medium) per Microsoft (MSRC Advisory).

The root cause is classified under CWE-359 (Exposure of Private Personal Information to an Unauthorized Actor), indicating that Microsoft Defender for Endpoint on macOS improperly exposes private personal data to local users who should not have access to it. The attack vector is local, requiring low privileges and no user interaction, with unchanged scope. An attacker with a standard local account on the affected macOS system could access sensitive information — such as personal data stored or processed by the Defender agent — without requiring elevated privileges. No detailed technical write-up or proof-of-concept exploit code with functional exploitation steps has been publicly confirmed (MSRC Advisory).

Successful exploitation results in a high confidentiality impact, with no effect on integrity or availability. A low-privileged local user on a macOS system running an affected version of Microsoft Defender for Endpoint could access private personal information handled by the security agent, potentially including user identity data, telemetry, or other sensitive artifacts. The scope is limited to the local system and does not directly enable lateral movement, but exposed data could be leveraged for further attacks or privacy violations (MSRC Advisory).

There is no confirmed active exploitation of CVE-2026-50657 in the wild. A GitHub repository (NeseOS-Corp/CVE-2026-50657) was identified as a purported PoC but was assessed as non-exploitable — containing only a README with vulnerability metadata and a LICENSE file, with no functional exploit code. CISA's SSVC assessment classifies exploitation as "none" and the vulnerability as not automatable. The EPSS score is approximately 0.0041 (low probability of exploitation). The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog (MSRC Advisory).

Microsoft has released a patch addressing this vulnerability. Users should update Microsoft Defender for Endpoint on macOS to version 101.26042.0020 or later. As interim measures, organizations should restrict local user access to systems running affected versions and monitor for unauthorized access to Defender processes or unexpected reads of sensitive data files. No configuration-based workaround has been published as an alternative to patching (MSRC Advisory).

The vulnerability was noted in coverage of Microsoft's July 2026 Patch Tuesday, which addressed a record 570 vulnerabilities including three zero-days. CVE-2026-50657 received limited individual attention given its medium severity and local-only attack vector. Coverage was primarily aggregated in Patch Tuesday roundup articles rather than dedicated security research posts (BleepingComputer, SANS ISC).