CVE-2026-49451
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThe 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 been confirmed across both JSON and YAML reader paths. This vulnerability is fixed in 2.7.5 and 3.5.4.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA stack overflow vulnerability exists in the OpenAPI.NET SDK (Microsoft.OpenApi) when parsing OpenAPI documents containing circular schema references. The library's JSON and YAML readers fail to properly detect or handle circular references during parsing, causing process termination. This DoS affects all public reader APIs in versions 2.0.0-preview11 through 2.7.5 and 3.5.4.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Microsoft.OpenApi package versionInspect your project's NuGet package reference (look for Microsoft.OpenApi in your .csproj file, packages.config, or run 'dotnet list package --include-transitive' in your project directory)Affected if The reported version falls within 2.0.0-preview11 through 2.7.5 or matches 3.5.4
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Locate OpenAPI parsing codeSearch your codebase for usage of OpenApi.NET readers such as OpenApiJsonReader, OpenApiYamlReader, or general document parsing calls that invoke the library's public reader APIsAffected if Your application code invokes any public reader APIs from Microsoft.OpenApi to parse JSON or YAML OpenAPI documents
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Assess document source trustDetermine whether the OpenAPI documents being parsed originate from untrusted or external sources (such as user uploads, API responses from third parties, or dynamically loaded schema files)Affected if Untrusted or externally-sourced OpenAPI documents are being parsed without prior validation
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Check for circular reference handlingInspect the OpenAPI documents currently processed by your system, or audit incoming documents for schema patterns where a $ref points back to an ancestor definition (for example, a schema referencing itself directly or through intermediate schemas)Affected if Circular schema references exist in the OpenAPI documents being parsed and the library version is within the affected range
You are affected if your environment uses Microsoft.OpenApi version 2.0.0-preview11 through 2.7.5 or version 3.5.4 and parses OpenAPI documents that may contain circular schema references, as this triggers the stack overflow in the library's reader components.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade Microsoft.OpenApi NuGet package to version 2.7.5, 3.5.4, or later. If immediate upgrade is not feasible, validate or sanitize incoming OpenAPI documents for circular references before parsing to prevent stack overflow.
2.7.5 (for 2.x branch) or 3.5.4 (for 3.x branch)
- Identify which version line of OpenAPI.NET SDK is in use (2.x or 3.x) by checking the package reference in the project
- For 2.x users: Update the Microsoft.OpenApi package reference to version 2.7.5 or later
- For 3.x users: Update the Microsoft.OpenApi package reference to version 3.5.4 or later
- Run NuGet restore to fetch the updated package
- Test that OpenAPI document parsing (both JSON and YAML) continues to work correctly with your documents
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing3.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-49451 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-49451 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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