{"id":"CVE-2026-59859","aliases":["GHSA-jqwh-526h-c92j"],"url":"https://o3.security/vulnerability/CVE-2026-59859","summary":"Kiota: Code Generation Literal Injection in the PHP Generator","details":"# Impact\n\nThe Kiota PHP code generator is vulnerable to a code generation literal injection attack. The generator embeds string values from OpenAPI fields (e.g. `description`, default values, and property names) directly into PHP double-quoted string literals without properly escaping the `$` character. Since PHP evaluates string interpolation expressions like `\"${expr}\"`, `\"$var\"`, and `\"{$obj->prop}\"` within double-quoted strings at runtime, an attacker who controls an OpenAPI specification file can inject arbitrary PHP code into generated model and request-builder classes.\n\n# Who is impacted\n\nDevelopers using Kiota to generate PHP API clients from external or untrusted OpenAPI specifications\n\nTeams with CI/CD pipelines configured to automatically regenerate client code from remote specs\n\nApplications that deploy generated PHP code to production servers\n\n# Vulnerability details\n\nAffected component: `StringExtensions.cs`\n\nRoot cause: The shared `SanitizeDoubleQuote()` function in `Writers/StringExtensions.cs` does not escape the `$` character. As a result, any schema-derived string emitted as a PHP double-quoted literal preserves `$`-prefixed interpolation constructs (`${...}`, `$var`, `{$...}`) verbatim, which PHP evaluates at runtime instead of treating as literal text. This is the same class of code-generation literal-injection flaw previously fixed for the Ruby generator (`#` interpolation), recurring here as a missed variant for PHP's `$` interpolation in the sibling sanitizer helper.\n\n# Attack vectors\n\nOpenAPI `description` and default fields in schema properties\n\nProperty wire-name keys embedded in deserializer/serializer methods\n\nAny schema-derived string embedded in PHP double-quoted literals\n\nSeverity: 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.\n\n# Patches\n\n[#7863](https://github.com/microsoft/kiota/pull/7863)\n\n# Workarounds\n\nIf you cannot upgrade immediately:\n\n1. Audit and sanitize OpenAPI specifications: Review all OpenAPI specification files for any descriptions, default values, or property names containing the `$` character. Remove or replace any suspicious strings before code generation.\n2. Code review of generated files: Implement mandatory code review of all generated PHP files before merging into any branch. Look for double-quoted strings containing `${`, `$var`, or `{$` patterns.\n3. Restrict specification sources: Only consume OpenAPI specifications from trusted internal sources. Avoid automatic code generation from external or third-party APIs until this patch is applied.\n4. Isolate generated code from production: Do not deploy generated PHP models to production environments unless the specification source has been verified and reviewed.\n5. Manual escaping (temporary): If regeneration is not possible, manually inspect and edit generated files to escape any `$` characters in double-quoted string literals (replace `$` with `\\$`).\n\n# Remediation\n\nUpgrade Kiota to 1.29.1, 1.32.4, or later.\n\nRegenerate/refresh existing generated clients as a precaution:\n\nRefreshing generated clients ensures previously generated vulnerable code is replaced with hardened output.","published":"2026-07-16T14:40:27.319Z","modified":"2026-10-07T07:05:31.137734548Z","cvss":null,"epss":{"score":0.01381,"percentile":0.70753,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"NuGet","name":"Microsoft.OpenApi.Kiota","fixedVersion":"1.32.4"},{"ecosystem":"NuGet","name":"Microsoft.OpenApi.Kiota.Builder","fixedVersion":"1.32.4"},{"ecosystem":"NuGet","name":"Microsoft.OpenApi.Kiota","fixedVersion":"1.29.1"},{"ecosystem":"NuGet","name":"Microsoft.OpenApi.Kiota.Builder","fixedVersion":"1.29.1"}],"fix":{"url":"https://github.com/microsoft/kiota/commit/5e2a211ac4261988fbdc72c3b268596ea8837b87","label":"microsoft/kiota@5e2a211"},"references":[{"type":"WEB","url":"https://github.com/microsoft/kiota/releases/tag/v1.32.4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59859.json"},{"type":"ADVISORY","url":"https://github.com/microsoft/kiota/security/advisories/GHSA-jqwh-526h-c92j"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59859"},{"type":"FIX","url":"https://github.com/microsoft/kiota/commit/5e2a211ac4261988fbdc72c3b268596ea8837b87"},{"type":"FIX","url":"https://github.com/microsoft/kiota/pull/7863"},{"type":"PACKAGE","url":"https://github.com/microsoft/kiota"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-07T07:05:31.137734548Z"}}