CVE-2026-71871: Orval: Import-time RCE via header-parameter default -> zod module-level template literal
Summary
Orval's zod schema generation emits the header-parameter default value as a module-level template literal (export const Default = <default>;) without escaping ${ or the backtick. A default of the form v${<code>}w injects a live JavaScript expression evaluated when the generated zod schema module is imported, executing attacker-controlled code at import — no request or function call needed. Verified on Orval 8.19.0; survives default OpenAPI validation.
Details
ts export const …Default = v${globalThis.ORVPWN()}w; // ${...} = arbitrary JS expression, runs at import
Malicious input: a header parameter with a default of v${<attacker JS>}w. ${...} permits any JS expression.
Note: this is one of several default-bearing positions that reach the same unescaped zod template-literal sink; a single fix (escape default values) closes all of them, and a CNA may choose to consolidate the related reports.
PoC
reproduce.sh (+ makespec.py) attached: generates the zod schema with default validation, bundles it, imports it, and shows a marker written at import. Verified on 8.19.0.
Impact
Code execution at import in any application that imports a zod schema module generated from an attacker-controlled or attacker-influenced OpenAPI description.
Suggested fix
Emit default values via a proper string-literal encoder (JSON.stringify, or escape backtick and ${ if a template literal must be used); never interpolate a spec value into a template literal. Apply to every default position. makespec.py reproduce.sh
Other sources
Orval generates type-safe JavaScript clients in TypeScript from OpenAPI v3 and Swagger v2 specifications. Prior to 8.21.0, a ${...} expression or backtick in a header parameter default is emitted into a module-level template literal emitted by zod schema generation without safe encoding. This permits attacker-controlled JavaScript to be evaluated when the generated zod schema module is imported, resulting in code execution in the developer, CI, test, or application environment. The affected code is packages/zod/src/index.ts function formatDefaultValue. This issue is fixed in version 8.21.0.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/orvalto a version that resolves this vulnerability.Fixed in 8.21.0 - Upgrade
Upgrade
Orvalto a version that resolves this vulnerability.Fixed in 8.21.0Patch Orval: Import-time RCE via header-parameter default -> zod module-level template literal - Configuration
When generating zod schema modules, ensure any OpenAPI `default` values are emitted via a proper string-literal encoder (JSON.stringify, or escape backtick and `${` if a template literal must be used). Do not interpolate spec `default` values into module-level template literals without escaping `${` and backticks. Apply the escaping to every `default` position.
Orval (zod schema generation) - packages/zod/src/index.ts (formatDefaultValue) default value encoding in module-level template literal export const …Default = `<default>` = Escape `${` and backticks when emitting defaults into template literals (e.g., use JSON.stringify or escape backtick and `${` if a template literal must be used)
Event History
Frequently Asked Questions
Who is exposed to this issue?
Users of Orval versions before 8.21.0 are exposed when they generate Zod schemas from an OpenAPI v3 or Swagger v2 specification containing a crafted header parameter default. The generated schema can execute code when it is imported in a developer, CI, test, or application environment.
What does an attacker need to exploit it?
An attacker needs control over, or the ability to influence, an API specification processed by Orval. The specification must include a header parameter default containing a ${...} expression or a backtick so that unsafe JavaScript is emitted into the generated module-level template literal.
How can I mitigate the issue if I cannot upgrade immediately?
Do not generate or import Zod schema output from untrusted or insufficiently reviewed OpenAPI or Swagger specifications. Review header parameter default values for backticks and ${...} expressions before running Orval generation or importing generated modules.
How can I determine whether generated output may already be affected?
Inspect generated Zod schema modules produced by versions before 8.21.0, especially output derived from header parameters with default values. Look for attacker-controlled content embedded in module-level template literals, including backticks or ${...} expressions.