The version of python3-tornado installed on the remote host is prior to 5.0.2-4. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2025-3109 advisory.

    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. (CVE-2025-67724)

    Tornado is a Python web framework and asynchronous networking library. In versions 6.5.2 and below, a     single maliciously crafted HTTP request can block the server's event loop for an extended period, caused     by the HTTPHeaders.add method. The function accumulates values using string concatenation when the same     header name is repeated, causing a Denial of Service (DoS).  Due to Python string immutability, each     concatenation copies the entire string, resulting in O(n2) time complexity. The severity can vary from     high if max_header_size has been increased from its default, to low if it has its default value of 64KB.
    This issue is fixed in version 6.5.3. (CVE-2025-67725)

    Tornado is a Python web framework and asynchronous networking library. Versions 6.5.2 and below use an     inefficient algorithm when parsing parameters for HTTP header values, potentially causing a DoS. The
    _parseparam function in httputil.py is used to parse specific HTTP header values, such as those in     multipart/form-data and repeatedly calls string.count() within a nested loop while processing quoted     semicolons. If an attacker sends a request with a large number of maliciously crafted parameters in a     Content-Disposition header, the server's CPU usage increases quadratically (O(n2)) during parsing. Due to     Tornado's single event loop architecture, a single malicious request can cause the entire server to become     unresponsive for an extended period. This issue is fixed in version 6.5.3. (CVE-2025-67726)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Detections

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Amazon Linux 2 : python3-tornado, --advisory ALAS2-2025-3109 (ALAS-2025-3109)

medium Nessus Plugin ID 281825

Version 1.3

Version 1.2

Version 1.1

Version 1.3 May 1, 2026, 7:22 AM IAVM reference Plugin Feed: 202605010722
Version 1.2 Jan 16, 2026, 10:12 PM IAVM reference STIG Severity (set to "I") Plugin Feed: 202601162212
Version 1.1 Jan 6, 2026, 10:00 AM New Plugin Feed: 202601061000