Microsoft OpenAPI.NET up to 2.7.4/3.5.3 recursion

Summaryinfo

A vulnerability marked as problematic has been reported in Microsoft OpenAPI.NET up to 2.7.4/3.5.3. The affected element is an unknown function. This manipulation causes recursion. This vulnerability is registered as CVE-2026-49451. Remote exploitation of the attack is possible. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Microsoft OpenAPI.NET up to 2.7.4/3.5.3. It has been declared as problematic. Affected by this vulnerability is an unknown code. The manipulation with an unknown input leads to a recursion vulnerability. The CWE definition for the vulnerability is CWE-674. The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack. As an impact it is known to affect availability. The summary by CVE is:

The OpenAPI.NET SDK contains a useful object model for OpenAPI documents in .NET along with common serializers to extract raw OpenAPI JSON and YAML documents from the model. From 2.0.0-preview11 until 2.7.5 and 3.5.4, a small OpenAPI document containing a circular schema reference can cause process termination through stack overflow in Microsoft.OpenApi. The issue affects OpenAPI document parsing through public OpenAPI.NET reader APIs and has been confirmed across both JSON and YAML reader paths. This vulnerability is fixed in 2.7.5 and 3.5.4.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-49451 since 05/30/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 06/30/2026). The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 2.7.5 or 3.5.4 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-40365). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Vendor

• Microsoft

Name

• OpenAPI.NET

Version

• 2.7.0
• 2.7.1
• 2.7.2
• 2.7.3
• 2.7.4
• 3.5.0
• 3.5.1
• 3.5.2
• 3.5.3

License

• commercial

Website

• Vendor: https://www.microsoft.com/
• Product: https://github.com/microsoft/OpenAPI.NET/

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Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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