CVE-2026-59860 in Kiota
Summary
by MITRE • 07/16/2026
Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.32.3, Kiota is affected by a code-generation injection vulnerability in the C# XML documentation-comment sink (the description, externalDocs label, and externalDocs link fields emitted as /// … comments). When text from an OpenAPI description is written into single-line XML doc comments without stripping newline and Unicode line-terminator characters, an attacker can break out of the /// comment line and inject additional code into generated C# clients. This issue is fixed in version 1.32.3.
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Analysis
by VulDB Data Team • 07/16/2026
The vulnerability in Kiota represents a critical code injection flaw that emerges from improper handling of XML documentation comments during C# client generation from OpenAPI specifications. This issue specifically affects the processing of description fields, externalDocs labels, and externalDocs links within the C# XML documentation-comment sink. When Kiota encounters text content from OpenAPI descriptions, it directly incorporates this data into single-line XML doc comments without adequate sanitization of special characters including newlines and Unicode line terminators. The absence of proper input validation creates a scenario where malicious actors can exploit the comment injection mechanism by embedding newline characters within their crafted payloads.
The technical exploitation occurs through the manipulation of XML documentation comment syntax in C# code generation. When OpenAPI description fields contain unescaped line terminators, these characters break out of the intended single-line /// comment structure and allow attackers to inject additional C# code or comments into the generated client libraries. This vulnerability directly maps to CWE-94, which describes the weakness of allowing code injection through improper handling of external input during code generation processes. The flaw essentially enables an attacker to modify the behavior of generated client code by injecting malicious content that gets embedded within the documentation comments section of the C# files.
The operational impact of this vulnerability extends beyond simple code modification as it can potentially compromise the security posture of applications relying on Kiota-generated clients. Attackers who control or influence the OpenAPI specifications used for code generation could inject malicious code that might execute during client operations, leading to unauthorized data access, command execution, or other security breaches within the consuming applications. This vulnerability affects any development workflow where automated C# client generation occurs from potentially untrusted OpenAPI sources, making it particularly dangerous in continuous integration environments or when integrating third-party API specifications.
Mitigation strategies should focus on implementing proper input sanitization and escaping mechanisms for all text content entering the XML documentation-comment generation pipeline. The fix implemented in version 1.32.3 addresses this by ensuring that newline and Unicode line-terminator characters are properly stripped or escaped before being inserted into single-line XML doc comments. Organizations should also consider implementing additional validation layers when processing OpenAPI specifications from external sources, including automated scanning for potentially malicious content patterns. This vulnerability aligns with ATT&CK technique T1059.006 which covers the use of command and scripting interpreters, as the injection could enable attackers to manipulate generated code behavior through documentation comment manipulation. The remediation approach should include comprehensive testing of the code generation pipeline against various input character sets to ensure that all special characters are properly handled during XML comment processing.