CVE-2026-44372

A redirect route rule like:

routeRules: {
  "/legacy/**": { redirect: "/**" }
}

is intended to rewrite paths within the same host. Before the patch, an attacker could turn the rewrite into a cross-host redirect by sliding an extra slash in after the rule prefix. Example exploit:

GET /legacy//evil.com

Nitro stripped /legacy from the matched pathname and joined the remainder against the rule's target. The remainder was //evil.com, which the join preserved verbatim, so Nitro responded with Location: //evil.com. Browsers resolve //evil.com as a protocol-relative URL against the current scheme, sending the user to https://evil.com.

Are you affected?

Users may be affected if all of the following are true:

1. Their project uses Nitro's routeRules with a redirect entry.
2. The target uses a /** wildcard suffix to forward sub-paths (e.g. redirect: "/**", redirect: "/new/**", proxy: { to: "http://upstream/**" }).
3. The redirect rule is not handled natively at the CDN layer. The vercel, netlify, cloudflare-pages, and edgeone presets translate routeRules.redirect into platform config (vercel.json, _redirects, EdgeOne v3 config) and serve the redirect at the edge, those deployments bypass the Nitro runtime entirely and are not affected. Every other preset executes the redirect through the Nitro runtime and can be vulnerable.

Patched versions

Upgrade to one of:

• 2.13.4 or later (or upgrade lockfile with latest ufo 1.6.4+)
• 3.0.260429-beta or later (https://github.com/nitrojs/nitro/pull/4236)

The fix has two parts:

1. ufo is bumped to ^1.6.4 (unjs/ufo@5cd9e67), which collapses any run of leading slashes to a single / inside withoutBase. This covers the typical "/scope/**" rule.
2. The Nitro runtime additionally collapses leading // before joining when the rule path itself is /** (in rare case which case withoutBase is never called and the raw pathname flows straight into joinURL("", …)).

Open redirect from any host serving Nitro with a wildcard redirect rule. The redirect target is fully attacker-controlled, the URL looks legitimate (it starts with the victim's domain), and the browser silently follows it.

Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.

CVE-2026-44372 has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. 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 (3.0.260429-beta, 2.13.4); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-44372? CVE-2026-44372 is a medium-severity open redirect vulnerability in nitro (npm), affecting versions < 3.0.260429-beta. It is fixed in 3.0.260429-beta, 2.13.4. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
2. How severe is CVE-2026-44372? CVE-2026-44372 has a CVSS score of 6.1 (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 packages are affected by CVE-2026-44372?
   • nitro (npm) (versions < 3.0.260429-beta)
   • nitropack (npm) (versions < 2.13.4)
4. Is there a fix for CVE-2026-44372? Yes. CVE-2026-44372 is fixed in 3.0.260429-beta, 2.13.4. Upgrade to this version or later.
5. Is CVE-2026-44372 exploitable, and should I be worried? Whether CVE-2026-44372 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-2026-44372 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-2026-44372?
   • Upgrade nitro to 3.0.260429-beta or later
   • Upgrade nitropack to 2.13.4 or later