TI-2026-36606 Aliases CVE-2026-49451 GHSA-v5pm-xwqc-g5wc

Microsoft.OpenAPI: Circular schema references may terminate OpenAPI parsing

HIGH 72CWE-674Published 2026-06-30 · Updated 2026-06-30

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-674.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00746 55th percentileScored 2026-11-07

Fix Fixed OpenAPI.NET (microsoft): 2.7.5, 3.5.4Microsoft.OpenApi (NuGet): 2.7.5, 3.5.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
Microsoft	OpenAPI.NET	2.0.0-preview11 to before 2.7.5; 3.0.0 to before 3.5.4	2.7.5, 3.5.4	Patch available	CNA
—	Microsoft.OpenApi (NuGet)	2.0.0-preview.11 to before 2.7.5	2.7.5	Patch available	GHSA-v5pm-xwqc-g5wc
—	Microsoft.OpenApi (NuGet)	3.0.0 to before 3.5.4	3.5.4	Patch available	GHSA-v5pm-xwqc-g5wc

OpenAPI.NET VendorMicrosoft Affected 2.0.0-preview11 to before 2.7.5; 3.0.0 to before 3.5.4 Fixed in 2.7.5, 3.5.4 Patch available CNA
Microsoft.OpenApi (NuGet) Vendor— Affected 2.0.0-preview.11 to before 2.7.5 Fixed in 2.7.5 Patch available GHSA-v5pm-xwqc-g5wc
Microsoft.OpenApi (NuGet) Vendor— Affected 3.0.0 to before 3.5.4 Fixed in 3.5.4 Patch available GHSA-v5pm-xwqc-g5wc

Remediation

Fix · CNA OpenAPI.NET (microsoft) Fixed in 2.7.5, 3.5.4
Fix · GHSA-v5pm-xwqc-g5wc Microsoft.OpenApi (NuGet) Fixed in 2.7.5 Advisory →
Fix · GHSA-v5pm-xwqc-g5wc Microsoft.OpenApi (NuGet) Fixed in 3.5.4 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-49451
2026-10-03 Alias added: GHSA-v5pm-xwqc-g5wc

References

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-49451

Other 2

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TI-2026-37256 Microsoft SharePoint Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8
TI-2026-26194 Windows Internet Key Exchange (IKE) Service Extensions Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8
TI-2026-16982 Microsoft SharePoint Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8
TI-2025-36863 Windows Server Update Service (WSUS) Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8
TI-2025-33671 Microsoft SharePoint Server Remote Code Execution Vulnerability KEVCVSS 3.1CRITICAL 9.8

See all 18045 →

Sources

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