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GHSA-v5pm-xwqc-g5wc

HighCVSS 7.5 / 10
Published Jun 30, 2026·Last modified Jul 6, 2026
Affected Components(0)

No affected components available

Description

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, <= 2.7.4
  • >= 3.0.0, <= 3.5.3

Patches

  • For the 2.X major version, versions 2.7.5 and above are patched.
  • For the 3.X major version, versions 3.5.4 and above are patched.
  • For the 1.X major version, the issue does not apply since that version of the library could not resolve references that pointed to another reference.

Impact

Applications, CLIs, developer tools, or services that parse untrusted OpenAPI documents in-process may be terminated by a crafted OpenAPI document containing circular schema references.

The impact is availability/process termination only. This report does not claim remote code execution, authentication bypass, credential exposure, privilege escalation, data exposure, or Microsoft hosted service impact.

Details

A standalone isolated-process harness confirmed repeatable process termination through public OpenAPI.NET reader APIs. The issue reproduces in the affected released NuGet packages and affects both JSON and YAML reader paths.

A separate Microsoft-owned local consumer, microsoft/kiota, also reproduces the termination through the kiota show --openapi <file> workflow. That workflow parses OpenAPI files in-process using Microsoft.OpenApi and Microsoft.OpenApi.YamlReader.

Example payload

{
    "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.

Risk Scores
Base Score
7.5

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.

Threat Intelligence
6.9

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.69%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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