CVE-2026-63345: Code Injection

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.

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Weakness Type (CWE)

CWE-94 CWE-94

CWE-1116 CWE-1116

References

Other 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

Frequently Asked Questions

What is CVE-2026-63345? +

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.

How do I check if I'm vulnerable to CVE-2026-63345? +

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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