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CVE-2026-96959

Microsoft Security Advisory CVE-2026-96959 - .NET and Visual Studio Denial of Service Vulnerability

Published Oct 13, 2026 · corrected/updated Oct 13, 2026 · evidence confidence medium

## Executive summary Microsoft 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. Signed 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. ## Announcement Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/489 ## CVSS Details - **Version:** 3.1 - **Severity:** High - **Score:** 7.5 - **Vector:** - **Weakness:** CWE-770 (Allocation of Resources Without Limits or Throttling) ## 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) | >= 10.0.0, = 11.0.0-preview.1, = 8.0.0, = 9.0.0, 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 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://doc

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2026-96959 is a high public vulnerability record for this product. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether this product is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: System.Security.Cryptography.Xml (>= 10.0.0, <= 10.0.12); System.Security.Cryptography.Xml (>= 11.0.0-preview.1, <= 11.0.0-rc.1); System.Security.Cryptography.Xml (>= 8.0.0, <= 8.0.4); System.Security.Cryptography.Xml (>= 9.0.0, <= 9.0.20). Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: CVSS 7.5. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-770. Sources contributing to this record: cve_org, github. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.

  • Patch and remediation

    No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 13, 2026 · GitHub Advisory Database

    Detected

    ## Executive summary Microsoft 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. Signed XML fixes add input-depth and operation-count limits, prohibit DTD processing by default, validate ent

  2. Oct 13, 2026 · GitHub Advisory Database

    Updated

    ## Executive summary Microsoft 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. Signed XML fixes add input-depth and operation-count limits, prohibit DTD processing by default, validate ent

Affected

  • nuget System.Security.Cryptography.Xml>= 10.0.0, <= 10.0.12
  • nuget System.Security.Cryptography.Xml>= 11.0.0-preview.1, <= 11.0.0-rc.1
  • nuget System.Security.Cryptography.Xml>= 8.0.0, <= 8.0.4
  • nuget System.Security.Cryptography.Xml>= 9.0.0, <= 9.0.20

Sources

References