CVE-2026-49451 json
Microsoft.OpenAPI: Circular schema references may terminate OpenAPI parsing
published 4mo ago modified 17d ago also GHSA-v5pm-xwqc-g5wc , EUVD-2026-40365
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.7%
- EPSS 0.7% chance of exploitation in 30 days, percentile 55%
- public exploits
- 0
- none known
Summary
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 been confirmed across both JSON and YAML reader paths. This vulnerability is fixed in 2.7.5 and 3.5.4.
Patch / fix
- nuget Microsoft.OpenApi 2.7.5, 3.5.4
Is CVE-2026-49451 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerCISA SSVC
- Exploitation
- Proof of concept is public
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 4mo ago
Exploit prediction
0.75% chance of exploitation in the next 30 days, higher than 55% of all scored CVEs (FIRST EPSS, 2026-11-11).
Exploits and checks
- github.com https://github.com/microsoft/OpenAPI.NET/security/advisories/GHSA-v5pm-xwqc-g5wc referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| GitHub | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| nuget | Microsoft.OpenApi | >=2.0.0-preview.11, <2.7.5 >=3.0.0, <3.5.4 |
2.7.5 3.5.4 |
Affected products
- microsoft OpenAPI.NET
Classification
- Weakness
-
- CWE-674 Uncontrolled Recursion
References
Sources
- CVE List CVE-2026-49451
- GitHub Advisory GHSA-v5pm-xwqc-g5wc
- NVD CVE-2026-49451
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