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ASP.NET Core Denial of Service Vulnerability

7.5HighCNA
Exploited
No known exploitation
Fix
Fixed in .NET 11.0 installed on Linux 11.0.0 · .NET 11.0 installed on Mac OS 11.0.0 · .NET 11.0 installed on Windows 11.0.0 · Microsoft Visual Studio 18.12.0 · Microsoft.Extensions.Validation 11.0.0
Who is exposed
Not reported

Do first: Upgrade to a fixed version: .NET 11.0 installed on Linux 11.0.0 · .NET 11.0 installed on Mac OS 11.0.0 · .NET 11.0 installed on Windows 11.0.0 · Microsoft Visual Studio 18.12.0 · Microsoft.Extensions.Validation 11.0.0.

Published
Last modified
Reference
Last checked
38/100 · provisional
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: yes
  • Technical impact: partial

Summary

Inefficient algorithmic complexity in ASP.NET Core allows an unauthorized attacker to deny service over a network.

cve.now Index

38Pcve.now Index 38 of 100 · methodology v3 · provisional
  • Exploitation0/40No signal
  • Exposure20/25No login or user action needed per the CVSS vector, CISA rates it automatable · Unknown: No advisory context yet
  • Reach10/20Affects NuGet packages
  • Severity7.5/10CVSS 7.5
  • No patch0/5No signal

What would change the score

  • Would score about 83 if added to CISA KEV
  • Would score about 78 if CISA's SSVC rates exploitation active
  • Would score about 43 if advisories confirm default setups are exposed

What to do

  • Upgrade to a fixed version: .NET 11.0 installed on Linux 11.0.0 · .NET 11.0 installed on Mac OS 11.0.0 · .NET 11.0 installed on Windows 11.0.0 · Microsoft Visual Studio 18.12.0 · Microsoft.Extensions.Validation 11.0.0.

Check your systems with an agent

Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.

Check whether my systems are affected by CVE-2026-118749 (ASP.NET Core Denial of Service Vulnerability), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-118749 (entry last updated 2026-11-10):
Affected:
- Microsoft .NET 11.0 installed on Linux: from 11.0.0-preview.1, fixed in 11.0.0
- Microsoft .NET 11.0 installed on Mac OS: from 11.0.0-preview.1, fixed in 11.0.0
- Microsoft .NET 11.0 installed on Windows: from 11.0.0-preview.1, fixed in 11.0.0
- Microsoft Microsoft Visual Studio 2026 version 18.12: from 18.12.0, fixed in 18.12.0
- Microsoft Microsoft.Extensions.Validation: from 11.0.0-rc.1.26425.128, fixed in 11.0.0
- NuGet package Microsoft.AspNetCore.App.Runtime.linux-arm: from 11.0.0-rc.1.26425.128, fixed in 11.0.0
- NuGet package Microsoft.AspNetCore.App.Runtime.linux-arm64: from 11.0.0-rc.1.26425.128, fixed in 11.0.0
- NuGet package Microsoft.AspNetCore.App.Runtime.linux-musl-arm: from 11.0.0-rc.1.26425.128, fixed in 11.0.0
- NuGet package Microsoft.AspNetCore.App.Runtime.linux-musl-arm64: from 11.0.0-rc.1.26425.128, fixed in 11.0.0
- NuGet package Microsoft.AspNetCore.App.Runtime.linux-musl-x64: from 11.0.0-rc.1.26425.128, fixed in 11.0.0
- and 7 more affected products, listed on https://cve.now/CVE-2026-118749
Fixed versions: 11.0.0, 18.12.0.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-118749 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-118749 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Packages (NuGet): find every lockfile in each project and run check_stack from the cve.now MCP server on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-118749
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-118749
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-118749.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: yes · Technical impact: partial

  3. Record last updated
  4. First seen by cve.now

Affected versions

  • Microsoft .NET 11.0 installed on Linux

    From 11.0.0-preview.1 · fixed in 11.0.0

  • Microsoft .NET 11.0 installed on Mac OS

    From 11.0.0-preview.1 · fixed in 11.0.0

  • Microsoft .NET 11.0 installed on Windows

    From 11.0.0-preview.1 · fixed in 11.0.0

  • Microsoft Microsoft Visual Studio 2026 version 18.12

    From 18.12.0 · fixed in 18.12.0

  • Microsoft Microsoft.Extensions.Validation

    From 11.0.0-rc.1.26425.128 · fixed in 11.0.0

  • From 11.0.0-rc.1.26425.128 · fixed in 11.0.0

    No fix released. The advisory names 11.0.0 as the fix, which the registry doesn't have yet.

  • From 11.0.0-rc.1.26425.128 · fixed in 11.0.0

    No fix released. The advisory names 11.0.0 as the fix, which the registry doesn't have yet.

  • From 11.0.0-rc.1.26425.128 · fixed in 11.0.0

    No fix released. The advisory names 11.0.0 as the fix, which the registry doesn't have yet.

Show all 17 packagesShow fewer packages

Evidence 3

Vendor advisory · 1

Establishes: Affected and fixed versions.

  1. Patch

CVE record · 2

Establishes: The identifier and description.

  1. Record
  2. Record

Corrections

None so far.

Something wrong on this page? Report an error. Every fix is listed here.

Questions about CVE-2026-118749

Is CVE-2026-118749 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data

Which versions are affected by CVE-2026-118749?

.NET 11.0 installed on Linux: from 11.0.0-preview.1 before 11.0.0. .NET 11.0 installed on Mac OS: from 11.0.0-preview.1 before 11.0.0. .NET 11.0 installed on Windows: from 11.0.0-preview.1 before 11.0.0. Microsoft Visual Studio 2026 version 18.12: from 18.12.0 before 18.12.0. Microsoft.Extensions.Validation: from 11.0.0-rc.1.26425.128 before 11.0.0. 12 more packages are listed on the page.Source: cve.now feed data

How do I fix CVE-2026-118749?

Upgrade to a fixed version: .NET 11.0 installed on Linux 11.0.0 · .NET 11.0 installed on Mac OS 11.0.0 · .NET 11.0 installed on Windows 11.0.0 · Microsoft Visual Studio 18.12.0 · Microsoft.Extensions.Validation 11.0.0.Source: cve.now feed data