CVE-2026-50658
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedTime-of-check time-of-use (toctou) race condition in Microsoft Defender allows an authorized attacker to elevate privileges locally.
In the news
Third-party coverage- Microsoft July 2026 Patch Tuesday fixes massive 570 flaws, 3 zero-days
- Microsoft CVE Summary - Bleeping Computer
Surfaced from public web coverage — external links open in a new tab.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceA time-of-check time-of-use (TOCTOU) race condition in Microsoft Defender allows an authorized local attacker to manipulate filesystem or registry operations during the gap between security checks and their execution, enabling local privilege escalation. The vulnerability exploits the interval between when Defender verifies a file's properties and when it actually processes that file.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 101.0.0, < 101.26042.0020CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- High
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check Microsoft Defender For Endpoint versionRun `Get-MpComputerStatus` in PowerShell and look for the `AntivirusSignatureVersion` or `AntivirusEngineVersion` field, or check the version via Windows Security app under AboutAffected if The installed version falls within 101.0.0 to 101.26042.0019 (any version >= 101.0.0 but less than 101.26042.0020)
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Verify local user account privilegesCheck if untrusted or standard user accounts have write access to locations Defender monitors (e.g., user-accessible folders, startup locations). Use `icacls` or review NTFS permissions on common executable paths.Affected if Standard or low-privilege users can write to directories or registry keys that Defender processes (the race condition requires manipulating files/registry during the check-to-use gap)
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Monitor for Defender-related process anomaliesUse Process Monitor or Windows Event Logs to observe MpDefender.exe or related Defender processes for unusual file handle operations, especially rapid create/write/delete sequences on the same fileAffected if Unusual patterns appear such as repeated file operations on the same object in quick succession, indicating possible TOCTOU exploitation attempts
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Review file system and registry integrityAudit recently created or modified executable files in Defender-monitored paths (e.g., startup folders, system32, Program Files). Use `Get-ChildItem` with recent timestamps or File Explorer sorting by date modified.Affected if Unexpected executables or scripts appear in locations Defender scans, especially if timestamps align with potential exploitation activity
You are affected if Microsoft Defender For Endpoint is installed at a version between 101.0.0 and 101.26042.0019 AND low-privilege users can manipulate files or registry keys in locations Defender monitors.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped101.26042.0020
Apply Microsoft security updates for Defender when released; until then, restrict local user permissions and monitor for suspicious Defender-related process behavior or file manipulation attempts.
Microsoft Defender For Endpoint version 101.26042.0020 or later
- Check current Microsoft Defender For Endpoint version by running: winver or opening Settings > About Windows
- Identify if version is >= 101.0.0 and < 101.26042.0020, which indicates vulnerability
- Update Microsoft Defender For Endpoint to version 101.26042.0020 or later through Microsoft 365 admin center, Windows Update, or your configured patch management solution
- Verify the update was successful by checking the version again after update completes
- Confirm the vulnerability is resolved
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,392.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-50658 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-50658 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data