{"id":"CVE-2026-96959","kind":"vulnerability","aliases":["CVE-2026-96959","GHSA-c399-9853-6jmj"],"related":[],"title":"Microsoft Security Advisory CVE-2026-96959 - .NET and Visual Studio Denial of Service Vulnerability","description":"## Executive summary\n\nMicrosoft is releasing this security advisory to provide information about a vulnerability in System.Security.Cryptography.Xml; System.Private.Xml. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.\n\nSigned XML fixes add input-depth and operation-count limits, prohibit DTD processing by default, validate entity references, bound encrypted-data candidate processing, and cap attributes and namespaces used by C14N transforms.\n\n## Announcement\n\nAnnouncement for this issue can be found at https://github.com/dotnet/announcements/issues/489\n\n## CVSS Details\n\n- **Version:** 3.1\n- **Severity:** High\n- **Score:** 7.5\n- **Vector:** `CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`\n\n- **Weakness:** CWE-770 (Allocation of Resources Without Limits or Throttling)\n## Affected Platforms\n\n- **Platforms:** Windows, Linux, macOS\n- **Architectures:** All\n\n## <a name=\"affected-packages\"></a>Affected Packages\n\nThe vulnerability affects Microsoft .NET projects that use an affected package version listed below.\n\nPackage name | Affected version | Patched version\n------------ | ---------------- | ---------------\n[System.Security.Cryptography.Xml](https://www.nuget.org/packages/System.Security.Cryptography.Xml) | >= 10.0.0, <= 10.0.12 | 10.0.13\n[System.Security.Cryptography.Xml](https://www.nuget.org/packages/System.Security.Cryptography.Xml) | >= 11.0.0-preview.1, <= 11.0.0-rc.1 | 11.0.0-rc.2\n[System.Security.Cryptography.Xml](https://www.nuget.org/packages/System.Security.Cryptography.Xml) | >= 8.0.0, <= 8.0.4 | 8.0.5\n[System.Security.Cryptography.Xml](https://www.nuget.org/packages/System.Security.Cryptography.Xml) | >= 9.0.0, <= 9.0.20 | 9.0.21\n\n## Advisory FAQ\n\n### <a name=\"how-affected\"></a>How do I know if I am affected?\n\nIf using a package listed in [affected packages](#affected-packages), you're exposed to the vulnerability.\n\n### <a name=\"how-fix\"></a>How do I fix the issue?\n\n1. 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.\n2. 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.\n\nOnce you have installed the updated runtime or SDK, restart your apps for the update to take effect.\n\nAdditionally, 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.\n\n## Other Information\n\n### Reporting Security Issues\n\nIf 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).\n\nSecurity 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.\n\n### Support\n\nYou 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.\n\n### Disclaimer\n\nThe 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.\n\n### External Links\n\n[CVE-2026-96959](https://www.cve.org/CVERecord?id=CVE-2026-96959)\n\n### Acknowledgements\n\n- novice-22\n- Ky0toFu (@ky0tofu)\n- Dr.-Ing Ashar Javed (@soaj1664ashar)\n\n### Revisions\n\nV1.0 (10/13/2026): Advisory published.","summary":"System.Security.Cryptography.Xml, a .NET library used for signed XML and C14N processing, lacks resource limits (CWE-770) on certain XML inputs, so processing can consume excessive resources. A remote attacker who can send crafted XML to an affected application can cause a denial of service, with no confidentiality or integrity impact per the CVSS vector.","severity":"high","cvss":7.5,"epss":0.007499999832361937,"exploited":false,"exploited_at":null,"products":[{"name":"System.Security.Cryptography.Xml","fixed":["10.0.13"],"affected":">= 10.0.0, <= 10.0.12","ecosystem":"nuget"},{"name":"System.Security.Cryptography.Xml","fixed":["11.0.0-rc.2"],"affected":">= 11.0.0-preview.1, <= 11.0.0-rc.1","ecosystem":"nuget"},{"name":"System.Security.Cryptography.Xml","fixed":["8.0.5"],"affected":">= 8.0.0, <= 8.0.4","ecosystem":"nuget"},{"name":"System.Security.Cryptography.Xml","fixed":["9.0.21"],"affected":">= 9.0.0, <= 9.0.20","ecosystem":"nuget"},{"name":"microsoft .net","fixed":["8.0.5"],"affected":">= 8.0.0, < 8.0.5","ecosystem":"vendor"},{"name":"microsoft .net","fixed":["9.0.21"],"affected":">= 9.0.0, < 9.0.21","ecosystem":"vendor"},{"name":"microsoft .net","fixed":["10.0.13"],"affected":">= 10.0.0, < 10.0.13","ecosystem":"vendor"},{"name":"microsoft .net","fixed":[],"affected":"= 11.0.0","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-770","dotnet","linux","macos","nuget","package","system.security.cryptography.xml","windows"],"not_affected_if":["no-system-security-cryptography-xml-reference","patched-versions","unaffected-version-range"],"how_to_check":"Search project files and lock files for a System.Security.Cryptography.Xml reference and note its version (affected: 8.0.0-8.0.4, 9.0.0-9.0.20, 10.0.0-10.0.12, 11.0.0-preview.1 to 11.0.0-rc.1).\nRun dotnet --info to list installed .NET SDK and runtime versions; the advisory says to update to the latest .NET.\nSelf-contained apps bundle their own copy and must be recompiled and redeployed.","fix":"Update the package reference to 8.0.5, 9.0.21, 10.0.13, or 11.0.0-rc.2 for the matching major line, or install the latest .NET.\nRecompile and redeploy self-contained applications, then restart apps after updating the runtime or SDK.","status":"open","published_at":"2026-10-13T19:22:08+00:00","first_seen_at":"2026-10-23T19:11:32+00:00","triaged_at":"2026-10-23T19:55:51+00:00","updated_at":"2026-10-23T23:44:52+00:00","category":"package","confidence":0.8,"triage":{"at":"2026-10-23T19:55:51Z","model":"claude-haiku-5-5","output":{"fix":"Update the package reference to 8.0.5, 9.0.21, 10.0.13, or 11.0.0-rc.2 for the matching major line, or install the latest .NET.\nRecompile and redeploy self-contained applications, then restart apps after updating the runtime or SDK.","summary":"System.Security.Cryptography.Xml, a .NET library used for signed XML and C14N processing, lacks resource limits (CWE-770) on certain XML inputs, so processing can consume excessive resources. A remote attacker who can send crafted XML to an affected application can cause a denial of service, with no confidentiality or integrity impact per the CVSS vector.","category":"package","who_cares":["nuget","dotnet","system.security.cryptography.xml","windows","linux","macos"],"confidence":0.8,"analyst_note":"","how_to_check":"Search project files and lock files for a System.Security.Cryptography.Xml reference and note its version (affected: 8.0.0-8.0.4, 9.0.0-9.0.20, 10.0.0-10.0.12, 11.0.0-preview.1 to 11.0.0-rc.1).\nRun dotnet --info to list installed .NET SDK and runtime versions; the advisory says to update to the latest .NET.\nSelf-contained apps bundle their own copy and must be recompiled and redeployed.","needs_analyst":false,"not_affected_if":["unaffected-version-range","patched-versions","no-system-security-cryptography-xml-reference"],"severity_if_unknown":"high"},"cost_usd":0.001008,"input_tokens":3916,"output_tokens":1232,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-2026':5A,16A,25A '-6':22A '-770':61B,84B,227C '-96959':6A,17A,26A '/av':216C '/corebounty.':525C '/dotnet/announcements)':555C '/dotnet/announcements/issues/489':204C '/dotnet/core/deploying/#self-contained-deployments-scd)':428C '/dotnet/runtime.':549C '/msrc/faqs-report-an-issue).':497C '/packages/system.security.cryptography.xml)':268C,275C,285C,292C '/report/vulnerability/new).':482C '1':329C '10.0.0':269C '10.0.12':270C '10.0.13':271C '11.0.0':276C,278C,280C '2':369C '3.1':208C,215C '7.5':212C '8.0.0':286C '8.0.4':287C '8.0.5':288C '9.0.0':293C '9.0.20':294C '9.0.21':295C '9853':21A 'add':161C 'addit':417C 'advisori':3A,130C,141C,296C,587C 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An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}