CVE-2026-73424

Astro: Unauthenticated path override in the @astrojs/vercel ISR function

if (hasValidMiddlewareSecret) {
  realPath = request.headers.get(ASTRO_PATH_HEADER);       // secret checked
} else if (request.headers.get('x-vercel-isr') === '1') {
  realPath = url.searchParams.get(ASTRO_PATH_PARAM);        // no secret checked
}

This affects apps that use @astrojs/vercel with isr: true and protect routes
at the edge. Two common setups are affected:

1. Path rules or firewall deny rules configured on Vercel (for example blocking
   /admin).
2. Split deployments (edgeMiddleware: true) where authorization lives in Astro
   middleware, since that middleware runs at the edge and not in the origin.

An attacker reads any GET rendered route by requesting
/_isr?x_astro_path=/the/protected/path. No credentials are required. The
protected content is produced by a fresh origin render, so the attack does not
depend on the response being cached first.

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2026-73424 has a CVSS score of 6.5 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (11.0.3); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

One option would be to require the secret again for path overrides, the way
PR #15959 did, so the ISR branch stops trusting the client supplied x_astro_path.
The 404 that PR #16079 was fixing would then need another approach that does not
rely on client input.

1. What is CVE-2026-73424? CVE-2026-73424 is a medium-severity missing authorization vulnerability in @astrojs/vercel (npm), affecting versions >= 10.0.3, < 11.0.3. It is fixed in 11.0.3. The application does not perform an authorization check before performing a sensitive operation.
2. How severe is CVE-2026-73424? CVE-2026-73424 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @astrojs/vercel are affected by CVE-2026-73424? @astrojs/vercel (npm) versions >= 10.0.3, < 11.0.3 is affected.
4. Is there a fix for CVE-2026-73424? Yes. CVE-2026-73424 is fixed in 11.0.3. Upgrade to this version or later.
5. Is CVE-2026-73424 exploitable, and should I be worried? Whether CVE-2026-73424 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-73424 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-73424? Upgrade @astrojs/vercel to 11.0.3 or later.

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