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.com/microsoft/kiota/pull/7746

Workarounds

If you cannot upgrade immediately:

1. Audit and sanitize OpenAPI specifications: Review all OpenAPI specification files for any default values or property names containing the # character. Remove or replace any suspicious strings before code generation.
2. Code review of generated files: Implement mandatory code review of all generated Ruby files before merging into any branch. Look for double-quoted strings containing #{, #$, or #@ patterns. 1....