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CVE-2026-72923 high CVSS 7.5

Vulnerability in Microsoft.OpenApi.YamlReader (CVE-2026-72923)

Summary

Vulnerability in Microsoft.OpenApi.YamlReader (CVE-2026-72923). Risk of unauthorized operations or information disclosure. Exploitable via YamlNode. Mitigation: upgrade to 2.12.0 or later.

Original description

The description as published by the source.

Impact

A small YAML OpenAPI document containing nested anchors and aliases can cause uncontrolled resource consumption in Microsoft.OpenApi.YamlReader and Microsoft.OpenApi.Readers. The issue affects OpenAPI document parsing through the public YAML reader APIs and can cause the parsing process to allocate excessive memory and terminate through out-of-memory conditions.

Affected versions

Microsoft.OpenApi.YamlReader

  • >= 2.0.0-preview.11, < 2.12.0
  • >= 3.0.0, < 3.10.0

Microsoft.OpenApi.Readers

  • < 1.6.30

Patches

  • For the 1.X major version, versions 1.6.30 and above are patched.
  • For the 2.X major version, versions 2.12.0 and above are patched.
  • For the 3.X major version, versions 3.10.0 and above are patched.

Impact

Applications, CLIs, developer tools, or services that parse untrusted YAML OpenAPI documents in-process may be terminated by a crafted YAML document containing nested anchors and aliases.

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

Microsoft.OpenApi.YamlReader and Microsoft.OpenApi.Readers parses YAML through SharpYaml. SharpYaml represents aliases as shared YamlNode instances in a directed acyclic graph, so the initial parsed YAML graph remains small. During conversion to System.Text.Json.Nodes.JsonNode, aliases must be materialized…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-72923 has been found in Microsoft.OpenApi.YamlReader.
Attackers can target a specific entry point like YamlNode over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade Microsoft.OpenApi.YamlReader to 2.12.0 or later.
If unsure, ask your IT team or search "Microsoft.OpenApi.YamlReader CVE-2026-72923" on the vendor's site.

CVE-2026-72923 (Microsoft.OpenApi.YamlReader) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: YamlNode / System.Text.Json.Nodes.JsonNode / JsonNode / OpenApiYamlReader.Read
Patched: 2.12.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-400) exists in Microsoft.OpenApi.YamlReader. Attackers reach the vulnerable code path via YamlNode without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of Microsoft.OpenApi.YamlReader. Attack surface: YamlNode / System.Text.Json.Nodes.JsonNode / JsonNode / OpenApiYamlReader.Read.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 2.12.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Microsoft.OpenApi.YamlReader' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'Microsoft.OpenApi.YamlReader' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Microsoft.OpenApi.YamlReader を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade Microsoft.OpenApi.YamlReader to 2.12.0

    ステージング環境で 2.12.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

nuget Microsoft.OpenApi.YamlReader
[{"type":"ECOSYSTEM","events":[{"introduced":"2.0.0-preview.11"},{"fixed":"2.12.0"}]}]
nuget Microsoft.OpenApi.Readers
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.6.30"}]}]

References

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