High advisory for Refitter
CVE-2026-63346 · Reported 30 Oct 2026
Full advisory details, affected packages, severity context, and original source.
Affected technology
Advisory overview
Refitter is a tool for generating a C# REST API client using the Refit library. Prior to 2.1.2, the header parameter name in `parameters[].name` with `in: header` is emitted verbatim into a Refit `[Header("<name>")]` attribute string without escaping quotation marks. An attacker-influenced OpenAPI description can pass default validation without `--skip-validation` and break out from the parameter-list position by closing the parameter and method syntax, attribute, interface, and namespace. The generated file can remain valid C# while containing a top-level file class with a `[ModuleInitializer]` method, which executes attacker code when the compiled assembly is loaded at application startup, even if the client is never called. Query `AliasAs` and enum/default value sinks are escaped; this flaw is in header-name attribute-string emission. The behavior was verified with Refitter 2.0.0 and .NET 8. This issue is fixed in version 2.1.2.
Related references
- https://github.com/christianhelle/refitter/commit/63a19b03699a9c267d6fab5f758ec26484db83a1
- https://github.com/christianhelle/refitter/pull/1178
- https://github.com/christianhelle/refitter/releases/tag/2.1.2
- https://github.com/christianhelle/refitter/security/advisories/GHSA-58x9-vjvp-6mx8
- https://github.com/user-attachments/files/29395048/maintainer-report.txt
- https://github.com/user-attachments/files/29395050/make_spec.py
- https://github.com/user-attachments/files/29395051/reproduce.sh