---
id: "CVE-2026-126347"
page: "https://infrastack.ai/live/CVE-2026-126347"
kind: "vulnerability"
aliases: ["CVE-2026-126347"]
title: "Tornado: crafted redirect paths send users to attacker-controlled hosts"
severity: "low"
cvss: 3.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["package", "python", "tornado", "web-apps"]
not_affected_if: ["static-redirect-targets", "tornado-6.6.1-or-later"]
published_at: "2026-11-12T22:19:19+00:00"
first_seen_at: "2026-11-12T22:40:37+00:00"
updated_at: "2026-11-12T22:42:35+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-126347", "first_seen_at": "2026-11-12T22:40:37+00:00"}]
exploit_sources: []
---

# Tornado: crafted redirect paths send users to attacker-controlled hosts

Link for people: https://infrastack.ai/live/CVE-2026-126347 (this .md is for agents)

Tornado's RedirectHandler can be tricked into sending a user to an attacker's site when a URL template lets attacker input shape the destination, using three or more leading slashes. Python and browsers parse such URLs differently, so the crafted destination reaches an outside host.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed Tornado version with `python -c "import tornado; print(tornado.version)"`
- Search the code for `RedirectHandler` and look for redirect URLs built from user-supplied values

## Fix

- Tornado: upgrade to `6.6.1`

## Timeline

- 2026-11-12T22:40:37+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-126347

## Documents

- [advisory] Vendor advisory: github.com https://github.com/tornadoweb/tornado/security/advisories/GHSA-5cjw-f85j-cv6r
- [fix] Patch: github.com https://github.com/tornadoweb/tornado/commit/c503241622c0efe7c40110d89834ce8b7fead1e4

## From the sources

Tornado is a Python web framework and asynchronous networking library. In versions through 6.6.0, applications using  tornado.web.RedirectHandler  with URL templates that allow attacker-controlled substitutions to influence the destination can be vulnerable to an open redirect using three or more leading slashes. Differences between Python’s URL parsing and browser URL interpretation allow a crafted destination to redirect a user to an attacker-controlled host. The remediation for CVE-2026-116578 in version 6.6.0 did not fully address this case. This issue is fixed in version 6.6.1.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_