Refitter is a tool for generating a C# REST API client using the Refit library

Why it is Yellow

• CVSS 8.6 high
• Remotely exploitable without logging in

References

• https://github.com/christianhelle/refitter/commit/793d2632899c2022511dfc15e30725ef69073973
• 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-3fhm-p725-h3g3
• https://github.com/user-attachments/files/29395228/maintainer-report.txt
• https://github.com/user-attachments/files/29395229/make_spec.py
• https://github.com/user-attachments/files/29395230/reproduce.sh

Original description

Refitter is a tool for generating a C# REST API client using the Refit library. Prior to 2.1.2, OpenAPI `paths`-object keys are emitted verbatim into Refit route attributes such as `[Get("<path>")]` without escaping quotation marks or restricting characters. An attacker-influenced single-line, slash-prefixed path survives default validation without `--skip-validation` and can close the attribute string, interface, and namespace while introducing a top-level file class and reopening the generated structure to keep valid C#. A `[ModuleInitializer]` method executes attacker code when an application compiles and loads the generated assembly at startup, even without calling the generated client. The enum and default value sinks are escaped and are not the vulnerable path-emission sink. The behavior was verified on Refitter 2.0.0 with .NET 8. This issue is fixed in version 2.1.2.