Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.0, Kiota's Ruby generator embedded OpenAPI default fields, property names, and other schema-derived strings through CodeMethodWriter.cs and SanitizeForQuotedLiteral() in Writers/StringExtensions.cs into Ruby double-quoted literals without escaping #, allowing attacker-controlled #{expr}, #$var, or #@var interpolation markers to inject arbitrary Ruby code into generated model classes. This issue is fixed in version 1.29.1 and 1.32.0.

Affected: NuGet: Microsoft.OpenAPI.Kiota, NuGet: Microsoft.OpenAPI.Kiota.Builder

Code Generation Literal Injection in Kiota Ruby Generator Leads to Arbitrary Code Execution

# Impact

The Kiota Ruby code generator is vulnerable to a code generation literal injection attack. The generator embeds string values from OpenAPI default fields and property names directly into Ruby double-quoted string literals without properly escaping the # character. Since Ruby evaluates string interpolation expressions like #{expr}, #$var, and #@var within double-quoted strings at runtime, an attacker who controls an OpenAPI specification file can inject arbitrary Ruby code into generated model classes.

# Who is impacted

Developers using Kiota to generate Ruby API clients from external or untrusted OpenAPI specifications Teams with CI/CD pipelines configured to automatically regenerate client code from remote specs Applications that deploy generated Ruby code to production servers

# Vulnerability details

Affected component: CodeMethodWriter.cs Root cause: The shared SanitizeForQuotedLiteral() function in Writers/StringExtensions.cs does not escape the # character

# Attack vectors

OpenAPI default fields in schema properties Property wire-name hash keys in deserializer/serializer methods Any schema-derived string embedded in Ruby double-quoted literals Severity: Critical when generated code reaches production; High for CI/CD environments with access to production secrets; Medium for public third-party specs; Low for developer-controlled specs.

# Patches

https://github.c…