CVE-2026-47300
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 · uneditedIncorrect implementation of authentication algorithm in ASP.NET Core allows an authorized attacker to elevate privileges over a network.
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 confidenceThis vulnerability exists in ASP.NET Core's authentication subsystem where an incorrect implementation of an authentication algorithm allows an already-authorized attacker to elevate their privileges. The flaw is network-exploitable and enables privilege escalation beyond the attacker's current authorized scope.
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>= 8.0.0, < 8.0.29>= 9.0.0, < 9.0.18>= 10.0.0, < 10.0.6>= 17.12.0, < 17.12.22>= 17.14.0, < 17.14.36>= 18.7.0, < 18.7.4CVSS 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
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/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.
-
Identify installed .NET runtime versionRun 'dotnet --version' in command prompt or PowerShell to get the .NET SDK/runtime versionAffected if Version is 8.0.0-8.0.28, 9.0.0-9.0.17, or 10.0.0-10.0.5 (any version within the affected ranges listed)
-
Confirm ASP.NET Core authentication is in useInspect project files (Program.cs, Startup.cs) or app settings (appsettings.json) for AddAuthentication(), AddAuthorization(), or authentication scheme configurations like JWT, cookie, or OAuthAffected if The application uses ASP.NET Core authentication middleware (any authentication scheme is configured)
-
Check for custom authorization policies or claims transformationSearch for AuthorizationHandler, IAuthorizationFilter, or custom policy implementations in the codebase. Review any ClaimsTransformation or IClaimsTransformation implementationsAffected if Custom authorization handlers, policy requirements, or claims transformation logic exist that could be exploited through the flawed algorithm
-
Verify Visual Studio version if used for developmentOpen Visual Studio, go to Help > About Microsoft Visual Studio, or run 'code --version' to check the installed Visual Studio versionAffected if Visual Studio 2022 version is 17.12.0-17.12.21 or 17.14.0-17.14.35, or Visual Studio 2026 version is 18.7.0-18.7.3
You are affected if you run a .NET version within the affected ranges AND your ASP.NET Core application uses the authentication subsystem with any configured auth scheme.
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.
From vendor data8.0.299.0.1810.0.6
Apply Microsoft security updates for ASP.NET Core immediately. Review and audit existing authentication configurations and role assignments for unexpected privilege escalations.
- Consultation8.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA8.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $12,352.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-47300 — 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-2026-47300 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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