---
id: CVE-2026-72923
title: >-
  In Microsoft.OpenApi.YamlReader from 2.0.0-preview.11 until 2.12.0 and from
  3.0.0 until 3.10.0, and in Microsoft.OpenApi.Readers prior to 1.6.30, a small
  YAML OpenAPI document containing nested anchors and aliases can cause
  uncontrolled …
summary: >-
  In Microsoft.OpenApi.YamlReader from 2.0.0-preview.11 until 2.12.0 and from
  3.0.0 until 3.10.0, and in Microsoft.OpenApi.Readers prior to 1.6.30, a small
  YAML OpenAPI document containing nested anchors and aliases can cause
  uncontrolled …
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-400
vendor: Microsoft
product: OpenApi.YamlReader
affected:
  - OpenApi.YamlReader >= 2.0.0-preview.11 < 2.12.0
  - OpenApi.YamlReader >= 3.0.0 < 3.10.0
  - OpenApi.Readers < 1.6.30
published: '2026-09-08'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T19:58:20.507'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-72923'
references:
  - url: >-
      https://github.com/microsoft/OpenAPI.NET/security/advisories/GHSA-7pxr-59rr-hqj2
    label: security-advisories@github.com
tags:
  - nvd
  - cve.org
epss: 0.012
epssPercentile: 0.66922
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-08T17:36:59.117131Z'
ingestedAt: '2026-09-08T19:08:49.624Z'
---

## Overview

In Microsoft.OpenApi.YamlReader from 2.0.0-preview.11 until 2.12.0 and from 3.0.0 until 3.10.0, and in Microsoft.OpenApi.Readers prior to 1.6.30, a small YAML OpenAPI document containing nested anchors and aliases can cause uncontrolled resource consumption when parsed through the public YAML reader APIs. YAML is parsed through SharpYaml, which represents aliases as shared nodes in a directed acyclic graph, so the parsed YAML graph stays small, but converting that graph to System.Text.Json.Nodes.JsonNode requires every alias to be materialized as an independent node because a JsonNode cannot be attached to multiple parents. Without a bound on that conversion work, a document with N nested anchors each referenced k times can require k^N materialized JSON nodes, leading to excessive memory allocation and process termination through out-of-memory conditions, a billion laughs style denial of service. The patched versions bound the YAML-to-JSON conversion by node count and nesting depth and report an OpenApiDiagnostic error instead of expanding without limit. This vulnerability is fixed in Microsoft.OpenApi.YamlReader 2.12.0 and 3.10.0, and Microsoft.OpenApi.Readers 1.6.30.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.