GHSA-6x36-qxmj-rv4p — System.Formats.Nrbf
HIGHGHSA-6x36-qxmj-rv4p is a high-severity (CVSS 7.5) CWE-409 vulnerability in System.Formats.Nrbf. A fix is available for System.Formats.Nrbf — see the affected versions and patch details below.
.NET Denial of Service Vulnerability
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-6x36-qxmj-rv4p.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-6x36-qxmj-rv4p plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
System.Formats.NrbfReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
Microsoft Security Advisory CVE-2024-43499 | .NET Denial of Service Vulnerability
<a name="executive-summary"></a>Executive summary
Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 9.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.
The NrbfDecoder component in .NET 9 contains a denial of service vulnerability due to incorrect input validation.
Announcement
Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/333
<a name="mitigation-factors"></a>Mitigation factors
Applications that do not use the NrbfDecoder component are not affected by this vulnerability. By default, .NET console apps and web apps do not reference this component.
<a name="affected-software"></a>Affected software
- Any .NET 9.0 application running on .NET 9.0.0.RC.2 or earlier.
<a name="affected-packages"></a>Affected Packages
The vulnerability affects any Microsoft .NET Core project if it uses any of affected packages versions listed below
<a name=".NET 9"></a>.NET 9
| Package name | Affected version | Patched version |
|---|---|---|
| System.Formats.Nrbf | <9.0.0 | 9.0.0 |
Advisory FAQ
<a name="how-affected"></a>How do I know if I am affected?
If you have a runtime or SDK with a version listed, or an affected package listed in affected software or affected packages, you're exposed to the vulnerability.
<a name="how-fix"></a>How do I fix the issue?
- To fix the issue please install the latest version of .NET 9.0 . If you have installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt you to update Visual Studio, which will also update your .NET SDKs.
- If your application references the vulnerable package, update the package reference to the patched version.
Note: You may need to take both actions. Upgrading to 9.0 GA is not by itself sufficient to resolve the vulnerability, since you could still be pulling in the vulnerable package by reference.
- If you have .NET 8.0 or greater installed, you can list the versions you have installed by running the
dotnet --infocommand. You will see output like the following;
.NET Core SDK (reflecting any global.json):
Version: 8.0.200
Commit: 8473146e7d
Runtime Environment:
OS Name: Windows
OS Version: 10.0.18363
OS Platform: Windows
RID: win10-x64
Base Path: C:\Program Files\dotnet\sdk\6.0.300\
Host (useful for support):
Version: 8.0.3
Commit: 8473146e7d
.NET Core SDKs installed:
8.0.200 [C:\Program Files\dotnet\sdk]
.NET Core runtimes installed:
Microsoft.NetCore.App 8.0.3 [C:\Program Files\dotnet\shared\Microsoft.NetCore.App]
Microsoft.AspNetCore.App 8.0.3 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.WindowsDesktop.App 8.0.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
To install additional .NET Core runtimes or SDKs:
https://aka.ms/dotnet-download
- If you're using .NET 9.0, you should download and install .NET 9.0 Runtime or .NET 9.0.100 SDK (for Visual Studio 2022 v17.12 latest Preview) from https://dotnet.microsoft.com/download/dotnet-core/9.0.
Once you have installed the updated runtime or SDK, restart your apps for the update to take effect.
Additionally, if you've deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.
Other Information
Reporting Security Issues
If you have found a potential security issue in .NET 9.0 or .NET 8.0, please email details to [email protected]. Reports may qualify for the Microsoft .NET Core & .NET 5 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 and https://github.com/dotnet/aspnet/. 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
Revisions
V1.0 (November 12, 2024): Advisory published.
Version 1.0
Last Updated 2024-11-12
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | System.Formats.Nrbf | all versions | 9.0.0dotnet add package System.Formats.Nrbf --version 9.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for System.Formats.Nrbf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update System.Formats.Nrbf to 9.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6x36-qxmj-rv4p is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-6x36-qxmj-rv4p can be triaged on real exposure rather than presence alone.
Tailored to GHSA-6x36-qxmj-rv4p. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Red Hat has the information for this vulnerability and its limitation to only .NET Core 9.0. No other versions are expected to be vulnerable to this flaw.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 9 | dotnet9.0-0:9.0.100-1.el9_5 | RHSA-2024:9543 |
Frequently Asked Questions
Is GHSA-6x36-qxmj-rv4p in your dependencies?
O3 Security finds GHSA-6x36-qxmj-rv4p across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.