CVE-2026-49803
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 · uneditedConcurrent execution using shared resource with improper synchronization ('race condition') in Windows AppX Deployment Service 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 race condition vulnerability exists in the Windows AppX Deployment Service where concurrent operations on shared resources lack proper synchronization. This allows an authorized local attacker to manipulate timing to elevate privileges to higher permission levels.
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< 10.0.14393.9339< 10.0.17763.9020< 10.0.19044.7548< 10.0.19045.7548< 10.0.26100.8875< 10.0.26200.8875< 10.0.28000.2269< 10.0.28000.2525all versions= r2CVSS 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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Identify Windows versionRun 'winver' or 'systeminfo | findstr /B /C:"OS Name" /C:"OS Version"' to obtain the installed Windows version and build numberAffected if The version and build number fall within any of these ranges: Windows 10 1607 < 10.0.14393.9339, Windows 10 1809 < 10.0.17763.9020, Windows 10 21h2 < 10.0.19044.7548, Windows 10 22h2 < 10.0.19045.7548, Windows 11 24h2 < 10.0.26100.8875, Windows 11 25h2 < 10.0.26200.8875, Windows 11 26h1 < 10.0.28000
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Confirm AppX Deployment Service presenceRun 'sc query AppXSvc' to verify the Windows AppX Deployment Service (AppXSvc) is installed and available on the systemAffected if The service exists on the system, indicating the vulnerable component is present
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Check user access to AppX deploymentAttempt to run 'Get-AppxPackage -AllUsers' or check if the current user account can access AppX deployment PowerShell cmdlets; also verify user is a local user with standard or elevated privilegesAffected if The user can execute AppX deployment commands, meaning they have access to the service interface where the race condition can be triggered
The system is affected if it runs any Windows version within the affected build ranges AND has the AppX Deployment Service available to the local user context.
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 · scoped10.0.14393.933910.0.17763.902010.0.19044.7548
Apply Microsoft security patches when available; alternatively, restrict user permissions to the AppX Deployment Service and monitor for suspicious deployment activities.
Upgrade to the specified build numbers or later via Windows Update: 10.0.14393.9339 (Win10 1607), 10.0.17763.9020 (Win10 1809), 10.0.19044.7548 (Win10 21h2), 10.0.19045.7548 (Win10 22h2), 10.0.26100.8875 (Win11 24h2), 10.0.26200.8875 (Win11 25h2), 10.0.28000.2525 (Win11 26h1); Windows Server 2012/R2
- Identify the current Windows build version by running `winver` or `systeminfo | findstr /B /C:"OS Name" /C:"OS Version"`
- For Windows 10: Navigate to Settings > Update & Security > Windows Update and install all available updates until you reach or exceed the required build number for your version
- For Windows 11: Navigate to Settings > Windows Update and install all available updates
- For Windows Server 2012/2012 R2: Since these versions are end-of-supported, Microsoft may not provide patches; consider migrating to a supported Windows Server version such as Windows Server 2022
- Alternatively, manually download the applicable Cumulative Update from the Microsoft Update Catalog matching your Windows version and build number
- After updating, verify the fix by checking the new build number matches or exceeds: Windows 10 1607: 10.0.14393.9339, Windows 10 1809: 10.0.17763.9020, Windows 10 21h2: 10.0.19044.7548, Windows 10 22h2: 10.0.19045.7548, Windows 11 24h2: 10.0.26100.8875, Windows 11 25h2: 10.0.26200.8875, Windows 11 26h1: 10.0.28000.2525
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-49803 — 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-2026-49803 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
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