Ruby Code Injection via OpenAPI Schema String Interpolation

Kiota is an OpenAPI based HTTP Client code generator. Prior to 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 1.32.0.

Casky was already ahead

This CVE exploits attack patterns that Casky's 322matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

Kiota is a code generator that transforms OpenAPI specifications into HTTP client libraries across multiple languages. Prior to version 1.32.0, the Ruby generator failed to properly escape special characters when embedding OpenAPI-derived strings (default values, property names, schema descriptions) into Ruby double-quoted literals. This allowed attackers to inject arbitrary Ruby code through unescaped interpolation markers like #{expr}, #$var, or #@var. The vulnerability affects developers using Kiota to generate Ruby clients from attacker-controlled or compromised OpenAPI specifications, potentially leading to arbitrary code execution in generated model classes. Organizations using Kiota in CI/CD pipelines or accepting external API definitions face particular risk.

Casky's 322 matching skills leverage Claude's extended reasoning to detect code injection attack patterns mapped to MITRE ATT&CK TA0001 (Reconnaissance) and TA0043 (Resource Development). Practitioners would see findings identifying: (1) unsafe handling of untrusted input in code generation workflows (CWE-94: Code Injection), (2) detection of interpolation syntax patterns in OpenAPI schemas that could escape into generated code, (3) analysis of code generator configurations accepting external API definitions without sanitization, and (4) runtime detection of suspicious Ruby string interpolation markers in generated model files. The skills enable practitioners to audit Kiota versions, validate OpenAPI input sources, and identify generated code containing potentially malicious interpolation expressions before deployment.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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322 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-59861.

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mobile security · low

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MITRE ATT&CK Techniques

TA0001 TA0043

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