Vulnerability · Published Jun 30, 2026 · Assigned by GitHub_M

CVE-2026-49451Microsoft.OpenAPI: Circular schema references may terminate OpenAPI parsing

High 7.5

In plain English

A high-severity security flaw in OpenAPI.NET from microsoft. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 55% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.7%top 45.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
NuGet	microsoft.openapi	2.7.5	GHSA-v5pm-xwqc-g5wc
NuGet	microsoft.openapi	3.5.4	GHSA-v5pm-xwqc-g5wc

Affected products (as reported)

Vendor	Product	Versions
microsoft	OpenAPI.NET	>= 2.0.0-preview11, < 2.7.5>= 3.0.0, < 3.5.4

Weakness: CWE-674 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/microsoft/OpenAPI.NET/security/advisories/GHSA-v5pm-xwqc-g5wc x_refsource_CONFIRM