CVE-2026-49451: The OpenAPI.NET SDK contains a useful object model for OpenAPI documents in .NET along with common serializers

Q: How do I fix CVE-2026-49451?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Q: Is CVE-2026-49451 being exploited?

CVE-2026-49451 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-49451 affect?

CVE-2026-49451 affects affected software. Severity is high (CVSS 7.5). The OpenAPI.NET SDK contains a useful object model for OpenAPI documents in .NET along with common serializers to extract raw OpenAPI JSON and YAML documents from the model. From 2.0.0-preview11 until 2.7.5 and 3.5.4, a small OpenAPI docume

Q: How urgent is CVE-2026-49451?

Priority 51/100. High severity; CISA SSVC: public proof of concept; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTE

CVE-2026-49451 is a high-severity flaw (CVSS 7.5) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The OpenAPI.NET SDK contains a useful object model for OpenAPI documents in .NET along with common serializers to extract raw OpenAPI JSON and YAML documents from the model. From 2.0.0-preview11 until 2.7.5 and 3.5.4, 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 bee

Why this priority

High severity
CISA SSVC: public proof of concept
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.2% (top 31%)
CISA exploited list	No
Weakness	CWE-674
Published	2026-06-30
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc.

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-06-30 17:16 UTCPublished CVE record published
2026-10-25 21:10 UTCUpdated Record last modified

Exact fixes by distribution

NuGet (.NET) · Microsoft.OpenAPI · FIXED · 3.5.4 · vulnerable: >= 3.0.0, <= 3.5.3 · source

dotnet add package Microsoft.OpenAPI --version 3.5.4

NuGet (.NET) · Microsoft.OpenApi · FIXED · 2.7.5 · vulnerable: >= 2.0.0-preview.11, <= 2.7.4 · source

dotnet add package Microsoft.OpenApi --version 2.7.5

Fedora 46 · log4cplus · FIXED · 2.2.0.1-2.fc46 · FEDORA-2026-fc241370c9 · source

sudo dnf upgrade --advisory=FEDORA-2026-fc241370c9

Fedora ELN · velocitty · FIXED · 1.0.3-2.eln159 · FEDORA-2026-edae8cd295 · source

sudo dnf upgrade --advisory=FEDORA-2026-edae8cd295

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-49451?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-49451 being exploited?

CVE-2026-49451 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-49451 affect?

CVE-2026-49451 affects affected software. Severity is high (CVSS 7.5). The OpenAPI.NET SDK contains a useful object model for OpenAPI documents in .NET along with common serializers to extract raw OpenAPI JSON and YAML documents from the model. From 2.0.0-preview11 until 2.7.5 and 3.5.4, a small OpenAPI docume

How urgent is CVE-2026-49451?

Priority 51/100. High severity; CISA SSVC: public proof of concept; Remotely exploitable, no login, no user action

References

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