CVE-2026-126347: Open Redirect (CVSS 3.1)

Description

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.

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CVSS v3.1 Score

3.1

LOW

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N

Weakness Type (CWE)

CWE-601 CWE-601

References

Other References

https://github.com/tornadoweb/tornado/commit/c503241622c0efe7c40110d89834ce8b7fead1e4 https://github.com/tornadoweb/tornado/security/advisories/GHSA-5cjw-f85j-cv6r

Frequently Asked Questions

What is CVE-2026-126347? +

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. It has a CVSS v3.1 base score of 3.1 (LOW).

How severe is CVE-2026-126347? +

CVE-2026-126347 has a CVSS v3.1 score of 3.1 out of 10, rated LOW. This is a low-severity vulnerability with limited impact.

How do I check if I'm vulnerable to CVE-2026-126347? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2026-126347