How severe is CVE-2026-44372?

No CVSS score has been assigned to CVE-2026-44372 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-44372?

CVE-2026-44372 affects the following packages: nitro (npm), nitropack (npm). Ecosystems affected: npm.

How do I fix CVE-2026-44372?

Update nitro to 3.0.260429-beta or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44372 is resolved across your whole dependency graph.

How do I detect CVE-2026-44372 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nitro, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-44372 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-44372?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-44372 can be triaged on real exposure rather than presence alone.

Is CVE-2026-44372 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-44372 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-44372?

CVE-2026-44372 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 21th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-44372?

CVE-2026-44372 is classified as Open Redirect (CWE-601). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-44372 published, and has it been updated?

CVE-2026-44372 was published on May 13, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-44372 — nitro

Fix: nitrojs/nitro#4236

CVE-2026-44372 is a Open Redirect vulnerability in nitro. A fix is available for nitro — see the affected versions and patch details below.

Nitro: Open Redirect via Protocol-Relative URL Bypass in Wildcard Route Rules

Also known asGHSA-9phm-9p8f-hw5m

Published

May 13, 2026

Updated

Aug 12, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Sep 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-44372.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs21th percentile — riskier than 21% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

57other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

nitronpm

12.0Mdownloads / week

nitropacknpm

1.6Mdownloads / week

Description

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:

Their project uses Nitro's routeRules with a redirect entry.
The target uses a /** wildcard suffix to forward sub-paths (e.g. redirect: "/**", redirect: "/new/**", proxy: { to: "http://upstream/**" }).
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.

Impact

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.

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:

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.
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("", …)).

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`nitro`	all versions	3.0.260429-beta`npm install nitro@3.0.260429-beta`
📦npm	`nitropack`	all versions	2.13.4`npm install nitropack@2.13.4`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nitro, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nitro to 3.0.260429-beta or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-44372 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-44372 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-44372. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

A redirect route rule like: ```ts 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 a

O3 Security · Impact-Aware SCA

Is CVE-2026-44372 in your dependencies?

O3 Security finds CVE-2026-44372 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works