tornadoweb tornado up to 6.5.2 RequestHandler.set_status Reason cross site scripting

Summaryinfo

A vulnerability categorized as problematic has been discovered in tornadoweb tornado up to 6.5.2. This impacts the function RequestHandler.set_status. Such manipulation of the argument Reason leads to cross site scripting. This vulnerability is uniquely identified as CVE-2025-67724. The attack can be launched remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in tornadoweb tornado up to 6.5.2 and classified as problematic. Affected by this issue is the function RequestHandler.set_status. The manipulation of the argument reason with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. CVE summarizes:

Tornado is a Python web framework and asynchronous networking library. In versions 6.5.2 and below, the supplied reason phrase is used unescaped in HTTP headers (where it could be used for header injection) or in HTML in the default error page (where it could be used for XSS) and can be exploited by passing untrusted or malicious data into the reason argument. Used by both RequestHandler.set_status and tornado.web.HTTPError, the argument is designed to allow applications to pass custom "reason" phrases (the "Not Found" in HTTP/1.1 404 Not Found) to the HTTP status line (mainly for non-standard status codes). This issue is fixed in version 6.5.3.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2025-67724 since 12/10/2025. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

The vulnerability scanner Nessus provides a plugin with the ID 278567 (Linux Distros Unpatched Vulnerability : CVE-2025-67724), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.5.3 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 9c163aebeaad9e6e7d28bac1f33580eb00b0e421 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at Tenable (278567). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• tornadoweb

Name

• tornado

Version

• 6.5.0
• 6.5.1
• 6.5.2

License

• open-source

Website

• Product: https://github.com/tornadoweb/tornado/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Once again VulDB remains the best source for vulnerability data.

Discussion