--- id: "CVE-2026-96222" kind: "vulnerability" aliases: ["CVE-2026-96222", "GHSA-vrv5-2jg9-4mmr"] title: "Microsoft Security Advisory CVE-2026-96222 - .NET Spoofing Vulnerability" severity: "high" cvss: 7.400000095367432 epss: 0.00570000009611249 exploited: false status: "open" category: "package" products: [{"name": "System.Security.Cryptography.Xml", "fixed": ["8.0.5"], "affected": ">= 8.0.0, <= 8.0.4", "ecosystem": "nuget"}, {"name": "microsoft windows 10 1607", "fixed": ["10.0.14393.9612"], "affected": "< 10.0.14393.9612", "ecosystem": "vendor"}, {"name": "microsoft windows 10 1809", "fixed": ["10.0.17763.9376"], "affected": "< 10.0.17763.9376", "ecosystem": "vendor"}, {"name": "microsoft windows server 2012", "fixed": [], "affected": "", "ecosystem": "vendor"}, {"name": "microsoft windows server 2012", "fixed": [], "affected": "= r2", "ecosystem": "vendor"}, {"name": "microsoft windows server 2016", "fixed": ["10.0.14393.9612"], "affected": "< 10.0.14393.9612", "ecosystem": "vendor"}, {"name": "microsoft windows server 2019", "fixed": ["10.0.17763.9376"], "affected": "< 10.0.17763.9376", "ecosystem": "vendor"}, {"name": "microsoft windows server 2022", "fixed": ["10.0.20348.5761"], "affected": "< 10.0.20348.5761", "ecosystem": "vendor"}, {"name": "microsoft windows server 2025", "fixed": ["10.0.26100.33650"], "affected": "< 10.0.26100.33650", "ecosystem": "vendor"}, {"name": "microsoft .net", "fixed": ["8.0.5"], "affected": ">= 8.0.0, < 8.0.5", "ecosystem": "vendor"}, {"name": "microsoft visual studio 2022", "fixed": ["17.14.42"], "affected": ">= 17.14.0, < 17.14.42", "ecosystem": "vendor"}, {"name": "microsoft visual studio 2026", "fixed": ["18.10.4"], "affected": ">= 18.10.0, < 18.10.4", "ecosystem": "vendor"}, {"name": "microsoft .net framework", "fixed": [], "affected": "= 4.8.1", "ecosystem": "vendor"}, {"name": "microsoft .net framework", "fixed": [], "affected": "= 4.8", "ecosystem": "vendor"}, {"name": "microsoft .net framework", "fixed": [], "affected": "= 4.6.2", "ecosystem": "vendor"}, {"name": "microsoft .net framework", "fixed": [], "affected": "= 4.7", "ecosystem": "vendor"}, {"name": "microsoft .net framework", "fixed": [], "affected": "= 4.7.1", "ecosystem": "vendor"}, {"name": "microsoft .net framework", "fixed": [], "affected": "= 4.7.2", "ecosystem": "vendor"}, {"name": "microsoft .net framework", "fixed": [], "affected": "= 3.5", "ecosystem": "vendor"}] ecosystems: ["nuget", "vendor"] tags: ["cwe-295", "dotnet", "linux", "macos", "nuget", "package", "windows", "xml-signature"] not_affected_if: ["does-not-use-keyinfox509data", "version-outside-8.0.0-to-8.0.4"] published_at: "2026-10-13T19:21:48+00:00" first_seen_at: "2026-10-23T19:11:32+00:00" updated_at: "2026-10-23T23:44:52+00:00" sources: [{"source": "ghsa", "url": "https://github.com/advisories/GHSA-vrv5-2jg9-4mmr", "first_seen_at": "2026-10-23T19:11:32+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-96222", "first_seen_at": "2026-10-23T23:44:52+00:00"}] --- # Microsoft Security Advisory CVE-2026-96222 - .NET Spoofing Vulnerability System.Security.Cryptography.Xml accepts serialized certificate formats with attacker-controlled chain metadata in KeyInfoX509Data instead of requiring a plain X.509 certificate. The advisory says this contributes to certificate-forgery and token-spoofing paths, so an attacker may be able to get forged signed XML or tokens accepted. _Summary, check and fix written by a model from the sources; labelled as such._ ## Affected - nuget:System.Security.Cryptography.Xml affected >= 8.0.0, <= 8.0.4 fixed 8.0.5 - vendor:microsoft windows 10 1607 affected < 10.0.14393.9612 fixed 10.0.14393.9612 - vendor:microsoft windows 10 1809 affected < 10.0.17763.9376 fixed 10.0.17763.9376 - vendor:microsoft windows server 2012 affected ? fixed ? - vendor:microsoft windows server 2012 affected = r2 fixed ? - vendor:microsoft windows server 2016 affected < 10.0.14393.9612 fixed 10.0.14393.9612 - vendor:microsoft windows server 2019 affected < 10.0.17763.9376 fixed 10.0.17763.9376 - vendor:microsoft windows server 2022 affected < 10.0.20348.5761 fixed 10.0.20348.5761 - vendor:microsoft windows server 2025 affected < 10.0.26100.33650 fixed 10.0.26100.33650 - vendor:microsoft .net affected >= 8.0.0, < 8.0.5 fixed 8.0.5 - vendor:microsoft visual studio 2022 affected >= 17.14.0, < 17.14.42 fixed 17.14.42 - vendor:microsoft visual studio 2026 affected >= 18.10.0, < 18.10.4 fixed 18.10.4 - vendor:microsoft .net framework affected = 4.8.1 fixed ? - vendor:microsoft .net framework affected = 4.8 fixed ? - vendor:microsoft .net framework affected = 4.6.2 fixed ? - vendor:microsoft .net framework affected = 4.7 fixed ? - vendor:microsoft .net framework affected = 4.7.1 fixed ? - vendor:microsoft .net framework affected = 4.7.2 fixed ? - vendor:microsoft .net framework affected = 3.5 fixed ? ## How to check dotnet list package --include-transitive | grep System.Security.Cryptography.Xml grep -ri "System.Security.Cryptography.Xml" --include=*.csproj --include=packages.lock.json . If the version is between 8.0.0 and 8.0.4 inclusive, the app is affected. ## Fix Update the System.Security.Cryptography.Xml package reference to 8.0.5 or later, or install the latest .NET patch release. Recompile and redeploy self-contained apps, then restart running apps. ## Timeline - 2026-10-23T19:11:32+00:00 ghsa https://github.com/advisories/GHSA-vrv5-2jg9-4mmr - 2026-10-23T23:44:52+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-96222 ## From the sources ## Executive summary Microsoft is releasing this security advisory to provide information about a vulnerability in System.Security.Cryptography.Xml. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. `KeyInfoX509Data` can accept serialized certificate formats containing attacker-controlled chain metadata instead of requiring a plain X.509 certificate, contributing to certificate-forgery and token-spoofing paths. ## Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/474 ## CVSS Details - **Version:** 3.1 - **Severity:** High - **Score:** 7.4 - **Vector:** `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N` - **Weakness:** CWE-295 (Improper Certificate Validation) ## Affected Platforms - **Platforms:** Windows, Linux, macOS - **Architectures:** All ## Affected Packages The vulnerability affects Microsoft .NET projects that use an affected package version listed below. Package name | Affected version | Patched version ------------ | ---------------- | --------------- [System.Security.Cryptography.Xml](https://www.nuget.org/packages/System.Security.Cryptography.Xml) | >= 8.0.0, <= 8.0.4 | 8.0.5 ## Advisory FAQ ### How do I know if I am affected? If using a package listed in [affected packages](#affected-packages), you're exposed to the vulnerability. ### How do I fix the issue? 1. To fix the issue please install the latest version of .NET. 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. 2. If your application references the vulnerable package, update the package reference to the patched version. You can list the versions you have installed by running the `dotnet --info` command. 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](https://docs.microsoft.com/dotnet/core/deploying/#self-contained-deployments-scd) 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 a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the [MSRC Researcher Portal](https://msrc.microsoft.com/report/vulnerability/new). Further information can be found in the MSRC [Report an Issue FAQ](https://www.microsoft.com/msrc/faqs-report-an-issue). 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-2026-96222](https://www.cve.org/CVERecord?id=CVE-2026-96222) ### Acknowledgements - Vaisha Bernard with Eye Security ### Revisions V1.0 (10/13/2026): Advisory published. --- _Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_