ASP.NET Core: Denial of service via unbounded resource allocation
Summary
Microsoft ASP.NET Core in .NET 11.0 pre-releases allows an unauthenticated remote attacker to cause a denial of service. The flaw is in Blazor static server-side rendering (SSR) client-side validation, which keeps attacker-controlled data in an unbounded cache and can exhaust server memory. The vector limits the impact to availability: no data theft or code execution is indicated.
Affected
- Microsoft .NET 11.0 pre-releases from 11.0.0-preview.1 before 11.0.0 on Linux, macOS and Windows (per the CNA record)
- Microsoft Visual Studio 2026 version 18.12 (the CNA record lists 18.12.0 to < 18.12.0, which is inconsistent; exact range unconfirmed)
- .NET 8, 9 and 10 are not listed as affected in the sources reviewed
Fixed in
- Upgrade .NET 11.0 to version 11.0.0 or later
- Visual Studio 2026 18.12: fixed version unknown
Workaround
- No vendor workaround found.
- Unverified: Microsoft documents an opt-out for static SSR client-side validation; it has not been confirmed to remove the vulnerable code path, so test before relying on it.
- Generic: rate limiting and request size limits at a reverse proxy or WAF in front of exposed .NET 11 applications.
Exploitation
- CISA SSVC: exploitation none, automatable yes, technical impact partial.
- Rapid7: exploitation less likely, not publicly disclosed.
- No public proof of concept or in-the-wild exploitation found.
Our recommendation
- Inventory .NET 11 pre-release installations and Visual Studio 2026 18.12 instances.
- Upgrade to .NET 11.0.0 or later once confirmed available for your release channel.
- Check build and deployment pipelines for .NET 11 pre-release SDKs and runtimes.
- Limit exposure of affected internet-facing applications until patched.
- Note: VulDB rates the issue 5.3 while other sources rate it 7.5 (CVSS 3.1).
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE Record (CVE Program) www.cve.org
- Microsoft Security Update Guide msrc.microsoft.com
- GitLab advisory mirror (NuGet package) advisories.gitlab.com
- .NET November 2026 servicing updates devblogs.microsoft.com
- Rapid7 Patch Tuesday November 2026 www.rapid7.com
- Strix CVE-2026-118748 www.strix.ai
- VulDB entry 435145 vuldb.com
- Microsoft Learn: Blazor client-side validation learn.microsoft.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 05:33.
Original description (NVD)
Allocation of resources without limits or throttling in ASP.NET Core allows an unauthorized attacker to deny service over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
Affected? We can help.
We check whether your systems are affected, install updates and close the gap – continuously with the System Health Checker if you wish.