CVE-2026-71871: Orval: Import-time RCE via header-parameter default -> zod module-level template literal

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.7%, percentile 51: FIRST’s model estimates a 0.7% chance of exploitation activity in the next 30 days, higher than 51% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes orval (npm) < 8.21.0, fixed in 8.21.0. Check your lockfile, including transitive dependencies.

What it is

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.

From the GitHub advisory

Summary

Orval's zod schema generation emits the header-parameter default value as a module-level template literal (export const Default = ;) without escaping ${ or the backtick. A default of the form v${ }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

Malicious input: a header parameter with a default of v${ }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.

Weakness type: CWE-94, CWE-116, CWE-1336.

Product: orval (npm) · Assigned by: GitHub_M · Published: 2026-08-19

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.65% probability of exploitation activity in the next 30 days; percentile 51.

Timeline

• 2026-08-19 — CVE record published by GitHub_M
• 2026-08-21 — CVE record last updated
• 2026-09-03 — GitHub-reviewed advisory GHSA-8j6p-r8jg-mxqh published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-8j6p-r8jg-mxqh github.com
2. CVE.org record CVE-2026-71871 cve.org
3. NVD entry CVE-2026-71871 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com

Critical npm advisories · Today’s Security Digest