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Amazon Linux 2023 : python3.13-tornado (ALAS2023-2026-1528)
high Nessus Plugin ID 304609
Synopsis
The remote Amazon Linux 2023 host is missing a security update.Description
It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-1528 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)
Tornado is a Python web framework and asynchronous networking library. In versions of Tornado prior to 6.5.5, the only limit on the number of parts in multipart/form-data is the max_body_size setting (default 100MB). Since parsing occurs synchronously on the main thread, this creates the possibility of denial-of- service due to the cost of parsing very large multipart bodies with many parts. This vulnerability is fixed in 6.5.5. (CVE-2026-31958)
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.
Solution
Run 'dnf update python3.13-tornado --releasever 2023.10.20260330' or or 'dnf update --advisory ALAS2023-2026-1528 --releasever 2023.10.20260330' to update your system.See Also
https://alas.aws.amazon.com//AL2023/ALAS2023-2026-1528.html
https://alas.aws.amazon.com/faqs.html
https://explore.alas.aws.amazon.com/CVE-2025-67724.html
https://explore.alas.aws.amazon.com/CVE-2025-67725.html
Plugin Details
Severity: High
ID: 304609
File Name: al2023_ALAS2023-2026-1528.nasl
Version: 1.1
Type: Local
Agent: unix
Published: 4/1/2026
Updated: 4/1/2026
Supported Sensors: Nessus Agent, Continuous Assessment, Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 4.4
CVSS v2
Risk Factor: Medium
Base Score: 6.4
Temporal Score: 4.7
Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:N
CVSS Score Source: CVE-2025-67724
CVSS v3
Risk Factor: Medium
Base Score: 6.1
Temporal Score: 5.3
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C
CVSS v4
Risk Factor: High
Base Score: 8.7
Threat Score: 6.6
Threat Vector: CVSS:4.0/E:U
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CVSS Score Source: CVE-2026-31958
Vulnerability Information
CPE: p-cpe:/a:amazon:linux:python3.13-tornado-debuginfo, p-cpe:/a:amazon:linux:python3.13-tornado-doc, p-cpe:/a:amazon:linux:python3.13-tornado, p-cpe:/a:amazon:linux:python3.13-tornado-debugsource, cpe:/o:amazon:linux:2023
Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list
Exploit Ease: No known exploits are available
Patch Publication Date: 4/1/2026
Vulnerability Publication Date: 12/12/2025
Reference Information
CVE: CVE-2025-67724, CVE-2025-67725, CVE-2025-67726, CVE-2026-31958