Source injection in Refitter via OpenAPI header parameter names
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Active
- Attack complexity
- Low
- Attack requirements
- None
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA. Impact type from CWE-94.
Summary
Refitter before 2.1.2 copies OpenAPI header parameter names into a Refit Header attribute without escaping quotation marks (CWE-116). An attacker who can influence the OpenAPI description can inject C# code into the generated client, which runs when the compiled assembly loads at application startup, even if the client is never called. Default validation does not block the crafted name.
Written with Claude Haiku 5.5 from the sources below · 2026-11-05
Description from the CNA
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| christianhelle | refitter | before 2.1.2 | 2.1.2 | Patch available | CNA |
- refitter Vendorchristianhelle Affected before 2.1.2 Fixed in 2.1.2 Patch available CNA
Remediation
Upgrade Refitter to version 2.1.2, which fixes this flaw.
Written with Claude Haiku 5.5 from the sources below · 2026-11-05
- Fix · CNA refitter (christianhelle) Fixed in 2.1.2
Timeline
- 2026-10-30 Threatist record created from CVE-2026-63346
- 2026-11-01 Priority changed: MEDIUM → LOW
- 2026-11-02 CISA SSVC decision points changed
- 2026-11-02 Priority changed: LOW → HIGH
References
Other 7
- https://github.com/christianhelle/refitter/security/advisories/GHSA-58x9-vjvp-6mx8
- https://github.com/christianhelle/refitter/pull/1178
- https://github.com/christianhelle/refitter/commit/63a19b03699a9c267d6fab5f758ec26484db83a1
- https://github.com/christianhelle/refitter/releases/tag/2.1.2
- 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
More christianhelle vulnerabilities
- TI-2026-83433 Code injection in Refitter via OpenAPI content-type map keys CVSS 4.0HIGH 8.6
- TI-2026-83423 Refitter OpenAPI $ref handling enables SSRF and local file inclusion CVSS 3.1HIGH 7.1
- TI-2026-83434 Code injection in Refitter C# client generator via OpenAPI path keys CVSS 4.0HIGH 8.6
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences