# CVE-2026-44373: Nitro: Proxy scope bypass via percent-encoded path traversal in `routeRules`

> Attackers can bypass proxy route rules using percent-encoded path traversal, causing requests to be forwarded outside the configured scope.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 13 May 2026
- **Updated:** 14 May 2026
- **Also known as:** GHSA-5w89-w975-hf9q

## What is CVE-2026-44373?

CVE-2026-44373 is a medium-severity path traversal vulnerability in nitrojs nitro, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Nitro is a next generation server toolkit. Prior to 3.0.260429-beta, an attacker could bypass a proxy route rule by sending percent-encoded path traversal (..%2f) in the URL, causing Nitro to forward a request that the upstream resolved outside the configured scope. This vulnerability is fixed in 3.0.260429-beta.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-44373?

4 open source packages ship an affected version, including nitro and nitropack. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nitro` | npm | All versions | 3.0.260429-beta |
| `nitro` | npm | All versions | 3.0.260429-beta |
| `nitropack` | npm | All versions | 2.13.4 |
| `nitropack` | npm | All versions | 2.13.4 |

Products: Nitro Nitro.

## How do I fix CVE-2026-44373?

Upgrade nitro to 3.0.260429-beta or later.

## Is CVE-2026-44373 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44373 exists.

## Other vulnerabilities in nitrojs nitro

- [CVE-2026-44372](https://insights.sbomify.com/CVE-2026-44372/): Nitro: Open Redirect via Protocol-Relative URL Bypass in Wildcard Route Rules (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-44373 and fix it if it is affected.

What it is: CVE-2026-44373 is a medium-severity path traversal vulnerability in nitrojs nitro, published on 13 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44373 exists.

Affected packages and fixed versions:
- nitro (npm): affected all versions; fixed in 3.0.260429-beta
- nitro (npm): affected all versions; fixed in 3.0.260429-beta
- nitropack (npm): affected all versions; fixed in 2.13.4
- nitropack (npm): affected all versions; fixed in 2.13.4

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-44373/ (Markdown: https://insights.sbomify.com/CVE-2026-44373/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44373
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44373
- OSV: https://osv.dev/vulnerability/CVE-2026-44373

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-44373/
Summaries are generated and may contain mistakes; the official description above is the record.