Vulnerability · Published Sep 8, 2026 · Assigned by GitHub_M
CVE-2026-72923Microsoft.OpenApi.YamlReader vulnerable to denial of service via YAML alias expansion
High 7.5
In plain English
A high-severity uncontrolled resource consumption in OpenAPI.NET from microsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.8% (higher than 79% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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. In Microsoft.OpenApi.Readers versions before 1.6.30 and Microsoft.OpenApi.YamlReader from 2.0.0-preview.11 through 2.11.0 and 3.0.0 through 3.9.0, parsing a YAML OpenAPI document with nested anchors and aliases can consume uncontrolled memory. SharpYaml represents aliases as shared nodes in a small directed acyclic graph, but conversion to independent OpenAPI or System.Text.Json.Nodes.JsonNode trees duplicates every aliased path; without a node-count or nesting-depth limit, N nested anchors referenced k times can require k^N materialized nodes and terminate the process through an out-of-memory condition. The fixed readers bound materialization to 5,000,000 nodes and a nesting depth of 64 by default and report an OpenApiDiagnostic error when a limit is exceeded. This vulnerability is fixed in Microsoft.OpenApi.Readers 1.6.30 and Microsoft.OpenApi.YamlReader 2.12.0 and 3.10.0.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| NuGet | microsoft.openapi.readers | 1.6.30 | GHSA-7pxr-59rr-hqj2 |
| NuGet | microsoft.openapi.yamlreader | 3.10.0 | GHSA-7pxr-59rr-hqj2 |
| NuGet | microsoft.openapi.yamlreader | 2.12.0 | GHSA-7pxr-59rr-hqj2 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| microsoft | OpenAPI.NET | >= 3.0.0, < 3.10.0>= 2.0.0-preview.11, < 2.12.0< 1.6.30 |
Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/microsoft/OpenAPI.NET/security/advisories/GHSA-7pxr-59rr-hqj2 x_refsource_CONFIRM
- https://github.com/microsoft/OpenAPI.NET/commit/1f9aea9bdcbf4066b59ce33b3bd8f97ed9cb4766 x_refsource_MISC
- https://github.com/microsoft/OpenAPI.NET/commit/21793261d6860fb6e607b71fd95c0bd320724764 x_refsource_MISC
- https://github.com/microsoft/OpenAPI.NET/commit/4db9af07d112cdf45170b7a946f956ffe74fa14e x_refsource_MISC