Refitter: C# source injection through OpenAPI content-type map keys
Refitter 2.0.0 and earlier can generate C# clients that run code at process startup when built from an attacker-controlled or attacker-influenced OpenAPI description. Fixed in 2.1.2.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Fix
- Fixed in 2.1.2
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Refitter, a .NET tool that generates C# REST API clients from OpenAPI specifications, is affected. A crafted content-type key in an OpenAPI description can inject arbitrary C# code into the generated client, which runs automatically when the generated assembly loads at application startup.
Summarized by anthropic/claude-haiku-5.5. Verify details against the original sources.
Read the original description
Refitter is a tool for generating a C# REST API client using the Refit library. Prior to 2.1.2, content-type keys in the content maps of `requestBody/responses` are emitted verbatim into a Refit `[Headers("Accept: <ct>", "Content-Type: <ct>")]` attribute string without escaping quotation marks. A crafted content-type key in an attacker-influenced OpenAPI description survives default validation without `--skip-validation`, breaks out of the attribute string and enclosing interface and namespace, and can introduce a top-level file class while leaving valid generated C#. A `[ModuleInitializer]` method in that class executes attacker code when the generated assembly is loaded at application startup, without requiring a call to the client. The behavior was verified with Refitter 2.0.0 and .NET 8. This issue is fixed in version 2.1.2.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- christianhelle refitter
fixed in 2.1.2
References 7
GitHub · christianhelle/refitter
GitHub · user-attachments/files
Questions about CVE-2026-63344
What does this mean?
A crafted OpenAPI content-type map key can inject C# source into the generated Refitter client. The injected code runs through a [ModuleInitializer] method when the compiled assembly loads, which is at process startup.Source: github.com
Am I affected, and how do I check?
Refitter versions 2.0.0 and earlier are affected, but only when the client is generated from an attacker-controlled or attacker-influenced OpenAPI description and that client is compiled into an application. To check, look at the Refitter version used to generate the client and where its OpenAPI description came from.Source: github.com
What should I do about it?
Upgrade Refitter to 2.1.2 or later and regenerate the client. Regenerating is needed because the vulnerable code is produced at generation time.Source: github.com
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data