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Vulnerability · Published Oct 30, 2026 · Assigned by GitHub_M

CVE-2026-63346Refitter: C# source injection through OpenAPI header parameter names

High 8.6

In plain English

A high-severity code injection in refitter from christianhelle. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 29% of all known vulnerabilities).

Severity (CVSS 4.0)8.6High
Exploit odds (30 days)0.4%top 71.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
christianhelle refitter < 2.1.2

Weakness: CWE-94, CWE-116 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References