GHSA-37gx-xxp4-5rgx BIT-dotnet-2026-33116 BIT-dotnet-sdk-2026-33116 CVE-2026-33116

Microsoft Security Advisory CVE-2026-33116 – .NET, .NET Framework, and Visual Studio Denial of Service Vulnerability

High NuGet

Severity: 7.5 / 10; High · CVSS 3.1
Exploit chance (EPSS): 2.14%; Chance of exploitation in the next 30 days. Higher than 82.06% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-20 Improper Input Validation; CWE-400 Uncontrolled Resource Consumption; CWE-835 Loop with Unreachable Exit Condition ('Infinite Loop')
Fix: 10.0.6; Upgrade System.Security.Cryptography.Xml to this version or later

Description

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.

A vulnerability exists in EncryptedXml class where an attacker can cause an infinite loop and perform a Denial of Service attack.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/392

CVSS Details

Version: 3.1
Severity: High
Score: 7.5
Vector: 7.5 CVSS: 3.1AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
Weakness: CWE-835 CWE-400 CWE-20: Loop with Unreachable Exit Condition ('Infinite Loop') Uncontrolled Resource Consumption Improper Input Validation

Affected Platforms

Platforms: All
Architectures: All

<a name="affected-packages"></a>Affected Packages

The vulnerability affects any Microsoft .NET project if it uses any of affected packages versions listed below

<a name=".NET 10"></a>.NET 10

Package name	Affected version	Patched version
System.Security.Cryptography.Xml	>=10.0.0, <=10.0.5	10.0.6

<a name=".NET 9"></a>.NET 9

Package name	Affected version	Patched version
System.Security.Cryptography.Xml	>=9.0.0, <=9.0.14	9.0.15

<a name=".NET 8"></a>.NET 8

Package name	Affected version	Patched version
System.Security.Cryptography.Xml	>=8.0.0, <=8.0.2	8.0.3

Advisory FAQ

<a name="how-affected"></a>How do I know if I am affected?

If using a package listed in affected packages, you're exposed to the vulnerability.

<a name="how-fix"></a>How do I fix the issue?

To update the Using the System.Security.Cryptography.xml NuGet package, use one of the following methods:

NuGet Package Manager UI in Visual Studio:

Open your project in Visual Studio.
Right-click on your project in Solution Explorer and select "Manage NuGet Packages..." or navigate to "Project > Manage NuGet Packages".
In the NuGet Package Manager window, select the "Updates" tab. This tab lists packages with available updates from your configured package sources.
Select the package(s) you wish to update. You can choose a specific version from the dropdown or update to the latest available version.
Click the "Update" button.

Using the NuGet Package Manager Console in Visual Studio:

Open your project in Visual Studio.
Navigate to "Tools > NuGet Package Manager > Package Manager Console".
To update a specific package to its latest version, use the following Update-Package command:

Update-Package -Id System.Security.Cryptography.xml

Using the .NET CLI (Command Line Interface):

Open a terminal or command prompt in your project's directory.
To update a specific package to its latest version, use the following add package command:

dotnet add package System.Security.Cryptography.xml

Once you have updated the nuget package reference you must recompile and deploy your application. Additionally we recommend you update your runtime and/or SDKs, but it is not necessary to patch the vulnerability.

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. Further information can be found in the MSRC Report an Issue FAQ.

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-2026-33116

Acknowledgements

Ludvig Pedersen

Revisions

V1.0 (April 14, 2026): Advisory published.

Affected versions

NuGet

Package	Vulnerable	Fixed in
System.Security.Cryptography.Xml	`>= 10.0.0, < 10.0.6`	`10.0.6`
System.Security.Cryptography.Xml	`>= 9.0.0, < 9.0.15`	`9.0.15`
System.Security.Cryptography.Xml	`>= 8.0.0, < 8.0.3`	`8.0.3`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

System.Security.Cryptography.Xml NuGet → `10.0.6`

dotnet

dotnet add package System.Security.Cryptography.Xml --version 10.0.6

Severity breakdown

CVSS 3.1 7.5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Weakness

CWE-20: Improper Input Validation

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How to prevent it

Architecture and Design: Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build "recognizers" for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses. [REF-1109] [REF-1110] [REF-1111]
Architecture and Design: Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
Architecture and Design, Implementation: Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
Architecture and Design: For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server. Even though client-side checks provide minimal benefits with respect to server-side security, they are still useful. First, they can support intrusion detection. If the server receives input that should have been rejected by the client, then it may be an indication of an attack. Second, client-side error-checking can provide helpful feedback to the user about the expectations for valid input. Third, there may be a reduction in server-side processing time for accidental input errors, although this is typically a small savings.
Implementation: When your application combines data from multiple sources, perform the validation after the sources have been combined. The individual data elements may pass the validation step but violate the intended restrictions after they have been combined.
Implementation: Be especially careful to validate all input when invoking code that crosses language boundaries, such as from an interpreted language to native code. This could create an unexpected interaction between the language boundaries. Ensure that you are not violating any of the expectations of the language with which you are interfacing. For example, even though Java may not be susceptible to buffer overflows, providing a large argument in a call to native code might trigger an overflow.
Implementation: Directly convert your input type into the expected data type, such as using a conversion function that translates a string into a number. After converting to the expected data type, ensure that the input's values fall within the expected range of allowable values and that multi-field consistencies are maintained.
Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control. Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.
Implementation: When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.

CWE-400: Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource.