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Vulnerability record/PUBLISHED/Published Oct 30, 2026 22:17:02 UTC

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.

Base score8.6/ 10
SeverityHighCVSS 4.0

Exploitability / impact

CVSS metric breakdown

Vector-derived attributes
Base severityHigh
Attack vectorNetworkAV
Attack complexityLowAC
Attack requirementsNoneAT
Privileges requiredNonePR
User interactionActiveUI
Vulnerable system confidentialityHighVC
Vulnerable system integrityHighVI
Vulnerable system availabilityHighVA
Subsequent system confidentialityNoneSC
Subsequent system integrityNoneSI
Subsequent system availabilityNoneSA
CVSS vector stringCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS communicates standardized severity and impact characteristics. It does not establish whether a system is exploitable in your specific environment.

Record context

CVE Numbering AuthorityGitHub_M
Last updatedOct 30, 2026 22:17:02 UTC
PublishedOct 30, 2026 22:17:02 UTC
ReservedJul 16, 2026 14:14:24 UTC