CVE-2026-63184
Refitter: Unrestricted OpenAPI references permit build-host SSRF and file inclusion
What happened?
Refitter is a tool for generating a C# REST API client using the Refit library. Prior to 2.1.1, the `refitter` dotnet tool invokes `NJsonSchema` with unsafe defaults for `$ref` resolution when generating Refit interfaces and contracts from attacker-controlled or attacker-influenced OpenAPI descriptions. Remote `http(s)` references cause requests from the developer or CI host and inline untrusted remote schema content into generated output. Absolute local file paths and relative `../` traversal outside the input directory also resolve and inline local content, permitting arbitrary local-file disclosure. The demonstrated chain stops at server-side request forgery, remote file inclusion, and local file inclusion, not code execution: Refit sets the base URL at runtime, enum values use verbatim-string doubling, and string defaults are escaped. This issue is fixed in version 2.1.1.
Affected software and versions
| Software | Version information | Fixed version |
|---|---|---|
| refitterchristianhelle | affected: < 2.1.1 | See vendor advisory |
Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.
Is it being exploited?
This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.
How to respond
- Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
- Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
- Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.
Sources and remediation references
- https://www.cve.org/CVERecord?id=CVE-2026-63184
- https://github.com/christianhelle/refitter/security/advisories/GHSA-x6w4-f264-3vvr
- https://github.com/christianhelle/refitter/pull/1173
- https://github.com/christianhelle/refitter/commit/6ad20a3803561225100b0a4bb6b12f947d23db7b
- https://github.com/christianhelle/refitter/releases/tag/2.1.1
- https://github.com/user-attachments/files/29395269/reproduce.sh
- https://github.com/user-attachments/files/29395271/maintainer-report.txt
- https://github.com/user-attachments/files/29395272/advisory.md
- https://github.com/user-attachments/files/29395283/reproduce.sh
- https://github.com/user-attachments/files/29395284/maintainer-report.txt
- https://github.com/user-attachments/files/29395285/advisory.md
- https://github.com/user-attachments/files/29395286/listener.py
- https://github.com/user-attachments/files/29395288/make_spec.py