GHSA-v5pm-xwqc-g5wc Microsoft.OpenAPI: Circular schema references may terminate OpenAPI parsing

• NuGet Microsoft.OpenApi: >= 2.0.0-preview.11, < 2.7.5 → fixed in 2.7.5 • NuGet Microsoft.OpenApi: >= 3.0.0, < 3.5.4 → fixed in 3.5.4

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-preview.11, = 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 version line they consume. Applications that parse OpenAPI documents from untrusted sources should avoid parsing those documents in the primary application process when possible. Running parsing in an isolated process can reduce the blast radius of parser failures.