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CVE-2026-120796

Microsoft Security Advisory CVE-2026-120796 - .NET Denial of Service Vulnerability

Products / packages Microsoft .NET 11.0 installed on Linux · Microsoft .NET 11.0 installed on Mac OS · Microsoft .NET 11.0 installed on Windows · 13 more

Published

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Severity and exploitation

Not in CISA KEVSource: MODERATE

KEV coverage does not rule out exploitation.

KEV checked 14/11/2026, 23:05:32 UTC
OSV · CVSS:3.1 · 5.3
Assessment vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:U/RL:O/RC:C
microsoft · CVSS:3.1 · 5.3
Assessment vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:U/RL:O/RC:C
The headline uses the highest imported catalog score. Assessments can differ by source and CVSS version.

Severity

medium5.3

CVSS measures technical severity, not the likelihood of an attack.

Known exploitation

Not listed in the checked CISA KEV catalog

Absence from CISA KEV does not rule out attacks.

Public exploit

Not established by this record

Missing evidence does not mean no public exploit exists.

Remediation

Package fixes recorded

Fix versions are recorded for 12 of 12 mapped packages. Check each release branch and any separate product guidance.

What this means

A denial of service vulnerability in .NET 11.0 allows an unauthorized attacker to deny service over a network due to inefficient algorithmic complexity. Affected versions include .NET 11.0 on Windows, Linux, and macOS, with versions between 11.0.0-preview.1 and 11.0.0-rc.3.26522.148.

Summarized by @cf/meta/llama-3.3-70b-instruct-fp8-fast. Verify details against the original sources.

Attack conditions

No attack-condition excerpt has been identified here. Review the full source description and references for authentication, network access, and configuration requirements.

Review supporting sources →

Affected versions

Check the exact model, release, and any platform requirements against your installation.

Microsoft · microsoft

.NET 11.0 installed on Linux

1 range
microsoft version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

11.0.0-preview.1 → before 11.0.0

custom versions

unaffected

unknown

Other versions: unknown

Microsoft · microsoft

.NET 11.0 installed on Mac OS

1 range
microsoft version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

11.0.0-preview.1 → before 11.0.0

custom versions

unaffected

unknown

Other versions: unknown

Microsoft · microsoft

.NET 11.0 installed on Windows

1 range
microsoft version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

11.0.0-preview.1 → before 11.0.0

custom versions

unaffected

unknown

Other versions: unknown

Microsoft · microsoft

System.Text.Json

1 range
microsoft version evidence

Compare with this publisher’s ranges. This does not inspect your installation.

affected

NOT_YET_AVAILABLE → before 11.0.0

custom versions

unaffected

unknown

Other versions: unknown

Packages

Compare each installed version with the publisher’s affected ranges. Where a fix is recorded, choose the appropriate release branch and test compatibility before upgrading.

System.Text.Json NuGet
Affected range Recorded fix
From 11.0.0-preview.1.26104.118 before 11.0.0Ecosystem versions11.0.0

Version evidence: OSV · GHSA-cpw3-h88j-9f6x

View original version evidence (0 explicit versions)

What to do

Compare your installed product and version with the affected versions above. A matching product name alone does not confirm exposure.

Use the recorded fix for your release branch. Review the publisher’s instructions and test compatibility before upgrading.

cve.new guidance unless attributed to a publisher. This page does not inspect your installation.

Public exploit evidence

No public exploit reference is identified in the imported evidence. This is not a claim that no exploit exists.

Original source description

Read the full publisher description

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET. This advisory provides guidance on updating affected applications and components.

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

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/499

CVSS Details

  • Version: 3.1
  • Severity: Medium
  • Score: 5.3 (base score)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:U/RL:O/RC:C
  • Weakness: CWE-407

Affected Platforms

  • Platforms: Windows, Linux, macOS
  • Architectures: All

<a name="affected-packages"></a>Affected Packages

The tables list affected version ranges and fixed package versions. Runtime and standalone deliveries are listed separately.

.NET 11.0 - affected runtime packages

Package Affected version Patched version
Microsoft.NETCore.App.Runtime.linux-arm >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.linux-arm64 >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.linux-musl-arm >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.linux-musl-arm64 >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.linux-musl-x64 >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.linux-x64 >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.osx-arm64 >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.osx-x64 >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.win-arm64 >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.win-x64 >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0
Microsoft.NETCore.App.Runtime.win-x86 >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0

Standalone System.Text.Json delivery

Package Affected version Patched version
System.Text.Json >= 11.0.0-preview.1.26104.118, <= 11.0.0-rc.3.26522.148 11.0.0

Advisory FAQ

<a name="how-affected"></a>How do I know if I am affected?

Check the deployed runtime and application package versions against the affected ranges above. Self-contained applications include their own runtime; updating a machine-wide runtime does not replace it.

<a name="how-fix"></a>How do I fix the issue?

Install the applicable runtime or update each independently referenced package to the fixed version above. Restart applications. Rebuild and redeploy self-contained applications; updating a machine-wide runtime does not replace their embedded runtime. An SDK update alone does not update an application's standalone package references.

Other Information

Reporting Security Issues

If you have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the MSRC Researcher Portal. Further information can be found in the MSRC Report an Issue FAQ.

Security reports made through MSRC may qualify for the Microsoft .NET Bounty. Details of the Microsoft .NET Bounty Program including terms and conditions are at https://aka.ms/corebounty.

Support

You can ask questions about this issue on GitHub in the .NET GitHub organization. The main repos are located at https://github.com/dotnet/runtime. The Announcements repo (https://github.com/dotnet/Announcements) will contain this bulletin as an issue and will include a link to a discussion issue. You can ask questions in the linked discussion issue.

Disclaimer

The information provided in this advisory is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.

External Links

CVE-2026-120796

Acknowledgements

  • Artur Stetsko

Revisions

V1.0 (November 10, 2026): Advisory published.

References

8 sources
msrc.microsoft.com/update-guide/vulnerability/CVE-2026-120796
Vendor advisorymicrosoft
dotnet/runtime · security/advisories/GHSA-cpw3-h88j-9f6x
Security advisory
nvd.nist.gov/vuln/detail/CVE-2026-120796
Security advisory
dotnet/announcements · issues/499
Source reference
dotnet/runtime · issues/137280
Source reference
dotnet/core · 11.0.0.md
Release notes
View 2 more references
dotnet/runtime · repository
Source reference
dotnet/runtime · releases/tag/v11.0.0
Release notes

Inside the record

Evidence available

Package identity
Version evidence
Remediation guidance · not supplied
Weakness classification
Additional publishers

Describes the evidence in this view, not whether the product is safe.

Original records

CVE-2026-120796

View the latest unmodified CVE JSON from the official source. It may be newer than this imported page.

cve.new JSON →

Underlying weaknesses

The source’s classification of what caused the vulnerability.

CWE-407 ↗

CWE-407: Inefficient Algorithmic Complexity

microsoft

Related →

Environment requirements

These conditions apply together as specified by the publisher. A matching product name alone does not establish exposure.

microsoft · platform conditions

Any condition may hold

Vulnerable product

cpe:2.3:a:microsoft:.net_11.0_installed_on_windows:*:*:*:*:*:*:*:*

From (inclusive): 11.0.0-preview.1

Before: 11.0.0

Vulnerable product

cpe:2.3:a:microsoft:.net_11.0_installed_on_linux:*:*:*:*:*:*:*:*

From (inclusive): 11.0.0-preview.1

Before: 11.0.0

Vulnerable product

cpe:2.3:a:microsoft:.net_11.0_installed_on_mac_os:*:*:*:*:*:*:*:*

From (inclusive): 11.0.0-preview.1

Before: 11.0.0

Vulnerable product

cpe:2.3:a:microsoft:system.text.json:*:*:*:*:*:*:*:*

From (inclusive): NOT_YET_AVAILABLE

Before: 11.0.0

Applicability preview
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  {
    "nodes": [
      {
        "operator": "OR",
        "negate": false,
        "cpeMatch": [
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:a:microsoft:.net_11.0_installed_on_windows:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "11.0.0-preview.1",
            "versionEndExcluding": "11.0.0"
          },
          {
            "vulnerable": true,
            "criteria": "cpe:2.3:a:microsoft:.net_11.0_installed_on_linux:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "11.0.0-preview.1",
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          {
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            "criteria": "cpe:2.3:a:microsoft:.net_11.0_installed_on_mac_os:*:*:*:*:*:*:*:*",
            "versionStartIncluding": "11.0.0-preview.1",
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          },
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]
Contributing organizations · 2
microsoft

Assigning organization

2026-11-13
CISA-ADP

Additional data publisher

2026-11-11

Timeline

All times UTC

  1. Advisory published

    Publication date supplied by the source.

  2. Source updated

    Latest modification date supplied by the source.

  3. Last imported by cve.new

    Latest catalog import, not the date we first saw this advisory.

What changed

Follow changes

Large field values are marked as truncated previews. Original source snapshots remain retained.