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

Impact 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 rea…

7.5CVSS Score

HIGHSeverity

NOCISA KEV

VulnerabilityImpact Type

📋 Vulnerability Details

CVE ID	CVE-2026-49451
Vendor	nuget
Affected Product	Microsoft.OpenAPI
Vulnerability Type	Vulnerability
CVSS Score	7.5 (HIGH)
Actively Exploited	❌ No known exploitation
Patch Status	See Vendor Advisory →
Reported By	CYBERDUDEBIVASH SENTINEL APEX Intelligence (via github_advisories)

🔬 Technical Analysis

Impact 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.

Affected versions - `>= 2.0.0-preview11, = 3.0.0,` workflow. That workflow parses OpenAPI files in-process using Microsoft.OpenApi and Microsoft.OpenApi.YamlReader.

Example payload ```json`

{ "openapi": "3.0.0", "info": { "title": "Test", "version": "0.0.1" }, "paths": {}, "components": { "schemas": { "A": { "$ref": "#/components/schemas/B" }, "B": { "$ref": "#/components/schemas/A" } } } } `

`Remediation Users should upgrade to Microsoft.OpenApi` 2.7.5 `or` 3.5.4`, depending on the major

🎯 Known Indicators of Compromise

{"type":"domain","value":"openapi.net","confidence_score":0.75,"first_seen":"2026-06-30","source_count":1}

📚 Advisory References

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