CVE-2026-41134: Kiota Code Generation Literal Injection Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2hx3-vp6r-mg3f",
  "modified" : "2026-08-17T14:58:37Z",
  "published" : "2026-04-14T23:39:41Z",
  "aliases" : [ "CVE-2026-41134" ],
  "summary" : "Kiota: Code Generation Literal Injection",
  "details" : "# CVE Advisory (CVE-2026-41134): Code Generation Literal Injection in Kiota\n\n## Summary\n\nKiota versions **prior to 1.29.1 and 1.31.1** are affected by a code-generation literal injection vulnerability in multiple writer sinks (for example: serialization/deserialization keys, path/query parameter mappings, URL template metadata, enum/property metadata, and default value emission).\n\nWhen malicious values from an OpenAPI description are emitted into generated source without context-appropriate escaping, an attacker can break out of string literals and inject additional code into generated clients.\n\n## Impact and Preconditions\n\nThis issue is only practically exploitable when:\n\n1. the OpenAPI description used for generation is from an **untrusted source**, or\n2. a normally trusted OpenAPI description has been **compromised/tampered with**.\n\nIf you only generate from trusted, integrity-protected API descriptions, risk is significantly reduced.\n\n## Affected Versions\n\n- **Affected:** all versions **< 1.29.1** and **>= 1.30.0, < 1.31.1**\n- **Fixed:** **1.29.1, 1.31.1,** and later\n\n## Illustrative Exploit Example\n\n### Example OpenAPI fragment (malicious default value)\n\n```yaml\nopenapi: 3.0.1\ninfo:\n  title: Exploit Demo\n  version: 1.0.0\ncomponents:\n  schemas:\n    User:\n      type: object\n      properties:\n        displayName:\n          type: string\n          default: \"\\\"; throw new System.Exception(\\\"injected\\\"); //\"\n```\n\n### Example generated C# snippet before fix (illustrative)\n\n```csharp\npublic User() {\n    DisplayName = \"\"; throw new System.Exception(\"injected\"); //\";\n}\n```\n\nThe injected payload escapes the intended string context and introduces attacker-controlled statements in generated code.\n\n> Note: this exploit is not limited to default values, but may also impact properties names (serialization), path or query parameters, enum representations and other locations.\n\n## Remediation\n\n1. Upgrade Kiota to **1.31.1 or later**.\n2. Regenerate/refresh existing generated clients as a precaution:\n\n```bash\nkiota update\n```\n\nRefreshing generated clients ensures previously generated vulnerable code is replaced with hardened output.\n\n## Acknowledgement\n\nWe would like to thank the researcher Thanatos Tian（Polyu) for finding this issue and for his contribution to this open source project.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.30.0"
      }, {
        "fixed" : "1.31.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota.Builder"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.30.0"
      }, {
        "fixed" : "1.31.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.29.1"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "Microsoft.OpenApi.Kiota.Builder"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.29.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/microsoft/kiota/security/advisories/GHSA-2hx3-vp6r-mg3f"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-41134"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/microsoft/kiota"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-94" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-14T23:39:41Z",
    "nvd_published_at" : "2026-04-22T21:17:09Z"
  }
}