CVE-2026-63346: Code Injection

Description

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.

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Weakness Type (CWE)

CWE-94 CWE-94

CWE-116 CWE-116

References

Other 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

Frequently Asked Questions

What is CVE-2026-63346? +

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.

How do I check if I'm vulnerable to CVE-2026-63346? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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