---
id: CVE-2026-59859
aliases:
  - GHSA-jqwh-526h-c92j
title: 'Microsoft Kiota: Code Generation Literal Injection in Kiota PHP Generator'
summary: 'Microsoft Kiota: Code Generation Literal Injection in Kiota PHP Generator'
severity: high
cwe:
  - CWE-94
vendor: Microsoft
product: Microsoft.OpenApi.Kiota
ecosystem: nuget
affected:
  - Microsoft.OpenApi.Kiota < 1.32.4
  - Microsoft.OpenApi.Kiota.Builder < 1.32.4
patched:
  - Microsoft.OpenApi.Kiota 1.32.4
  - Microsoft.OpenApi.Kiota.Builder 1.32.4
published: '2026-07-24'
updated: '2026-07-24'
source: GHSA
sourceUrl: 'https://github.com/advisories/GHSA-jqwh-526h-c92j'
references:
  - url: 'https://github.com/microsoft/kiota/security/advisories/GHSA-jqwh-526h-c92j'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-59859'
  - url: 'https://github.com/microsoft/kiota/pull/7863'
  - url: >-
      https://github.com/microsoft/kiota/commit/5e2a211ac4261988fbdc72c3b268596ea8837b87
  - url: 'https://github.com/microsoft/kiota/releases/tag/v1.32.4'
  - url: 'https://github.com/advisories/GHSA-jqwh-526h-c92j'
tags:
  - ghsa
  - nuget
epss: 0.01381
epssPercentile: 0.7098
ingestedAt: '2026-07-24T16:33:09.866Z'
---

## Overview

# Impact

The 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.

# Who is impacted

Developers using Kiota to generate PHP 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 PHP code to production servers

# Vulnerability details

Affected component: `StringExtensions.cs`

Root 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.

# Attack vectors

OpenAPI `description` and default fields in schema properties

Property wire-name keys embedded in deserializer/serializer methods

Any schema-derived string embedded in PHP 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

[#7863](https://github.com/microsoft/kiota/pull/7863)

# Workarounds

If you cannot upgrade immediately:

1. Audit and sanitize OpenAPI specifications: Review all OpenAPI specification files for any descriptions, default values, or property names containing the `$` character. Remove or replace any suspicious strings before code generation.
2. Code review of generated files: Implement mandatory code review of all generated PHP files before merging into any branch. Look for double-quoted strings containing `${`, `$var`, or `{$` patterns.
3. 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.
4. Isolate generated code from production: Do not deploy generated PHP models to production environments unless the specification source has been verified and reviewed.
5. 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 `\$`).

# Remediation

Upgrade Kiota to 1.32.4 or later.

Regenerate/refresh existing generated clients as a precaution:

Refreshing generated clients ensures previously generated vulnerable code is replaced with hardened output.

## Affected packages

- `Microsoft.OpenApi.Kiota < 1.32.4`
- `Microsoft.OpenApi.Kiota.Builder < 1.32.4`

## Remediation

Upgrade to a patched release:

- `Microsoft.OpenApi.Kiota 1.32.4`
- `Microsoft.OpenApi.Kiota.Builder 1.32.4`