Microsoft.OpenApi.YamlReader vulnerable to denial of service via YAML alias expansion

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-72923: 1.85% estimated exploitation activity in the next 30 days; percentile 79.07 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

14 Oct 2026, 20:11 UTC

Last modified by the source

14 Oct 2026, 20:15 UTC

Source last checked

26 Oct 2026, 17:05 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-7pxr-59rr-hqj2

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-7pxr-59rr-hqj2

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# Patch Next advisory brief: CVE-2026-72923

Advisory: Microsoft.OpenApi.YamlReader vulnerable to denial of service via YAML alias expansion
IDs: CVE-2026-72923, GHSA-7pxr-59rr-hqj2
Record: https://patchnext.com/advisories/cve-2026-72923 (revision 2, source checked 26 Oct 2026, 17:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: microsoft.openapi.yamlreader 3.10.0, 2.12.0; microsoft.openapi.readers 1.6.30. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet microsoft.openapi.yamlreader: affected >= 3.0.0, < 3.10.0; >= 2.0.0-preview.11, < 2.12.0; fixed in 3.10.0, 2.12.0
- NuGet microsoft.openapi.readers: affected < 1.6.30; fixed in 1.6.30

## Suggested inspection (read-only)
- NuGet microsoft.openapi.yamlreader: check the installed version with your package manager.
- NuGet microsoft.openapi.readers: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on microsoft.openapi.yamlreader, microsoft.openapi.readers.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-7pxr-59rr-hqj2 (OSV record GHSA-7pxr-59rr-hqj2 lists affected ranges: NuGet microsoft.openapi.yamlreader >=3.0.0 =2.0.0-preview.11 =0 <1.6.30 (fixed))
- Verified: https://github.com/advisories/GHSA-7pxr-59rr-hqj2 (GitHub-reviewed advisory GHSA-7pxr-59rr-hqj2 lists affected ranges: NuGet microsoft.openapi.yamlreader >=3.0.0 =2.0.0-preview.11 =0 <1.6.30)

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