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Kiota: Code Generation Literal Injection in the PHP Generator

Collected exploitation and prediction evidence

Risk source coverage

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

CVE-2026-59859

Exact risk observation. Current source statements above are a separate evidence layer. Latest risk evidence.

No KEV entry is attached to this observation; this is not evidence that exploitation is absent.

FIRST EPSS: 1.38 % · percentile 71.97 % · scored 24 Oct 2026. Retained older prediction.

Observed 25 Oct 2026 02:24:38 UTC · Complete immutable risk JSON

cve-program · CVE-2026-59859

Published

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.4, Kiota's PHP generator embedded OpenAPI description, default fields, property names, and other schema-derived strings into PHP double-quoted literals through SanitizeDoubleQuote() in Writers/StringExtensions.cs without escaping $, allowing attacker-controlled ${...}, $var, or {$obj->prop} interpolation constructs to inject arbitrary PHP code into generated model and request-builder classes. This issue is fixed in version 1.29.1 and 1.32.4.

Source published
16 Jul 2026 14:40:27 UTC
Source modified
17 Aug 2026 15:02:29 UTC
Observed here
23 Oct 2026 15:48:27 UTC
Source terms
CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

nvd · CVE-2026-59859

Published

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.4, Kiota's PHP generator embedded OpenAPI description, default fields, property names, and other schema-derived strings into PHP double-quoted literals through SanitizeDoubleQuote() in Writers/StringExtensions.cs without escaping $, allowing attacker-controlled ${...}, $var, or {$obj->prop} interpolation constructs to inject arbitrary PHP code into generated model and request-builder classes. This issue is fixed in version 1.29.1 and 1.32.4.

NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON.

Source analysis status: Deferred

Weakness classifications: CWE-94

Original publisher date fields

published: 2026-07-16T15:16:35.167

lastModified: 2026-10-24T21:10:00.130

Source published
16 Jul 2026 15:16:35 UTC
Source modified
24 Oct 2026 21:10:00 UTC
Observed here
25 Oct 2026 14:19:22 UTC
Source terms
NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

osv · GHSA-jqwh-526h-c92j

Published

# 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 1.29.1, 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.

Source published
24 Jul 2026 15:46:46 UTC
Source modified
17 Aug 2026 15:00:08 UTC
Observed here
23 Oct 2026 16:01:25 UTC
Source terms
GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Publisher rating · HIGH

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Sources read 27 Oct 10:14 UTC · 272 of 272 readable · 271 fully read · documentation 469/469 current