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[USN-7950-1] Tornado vulnerabilities

Posted on 08 January 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-7950-1
January 08, 2026

python-tornado vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 25.10
- Ubuntu 25.04
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in Tornado.

Software Description:
- python-tornado: scalable, non-blocking web server and tools

Details:

It was discovered that Tornado incorrectly handled special characters in
HTTP headers. An attacker could possibly use this issue to execute a cross-
site scripting (XSS) attack. This issue only affected Ubuntu 20.04 LTS,
Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, Ubuntu 25.04, and Ubuntu 25.10.
(CVE-2025-67724)

It was discovered that Tornado incorrectly handled repeated HTTP headers.
An attacker could possibly use this issue to cause Tornado to use excessive
resources, causing a denial of service. (CVE-2025-67725)

It was discovered that Tornado incorrectly handled parsing of certain HTTP
header values. An attacker could possibly use this issue to cause Tornado
to use excessive resources, causing a denial of service. (CVE-2025-67726)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 25.10
python3-tornado 6.4.2-3ubuntu0.2

Ubuntu 25.04
python3-tornado 6.4.2-1ubuntu0.25.04.3

Ubuntu 24.04 LTS
python3-tornado 6.4.0-1ubuntu0.4

Ubuntu 22.04 LTS
python3-tornado 6.1.0-3ubuntu0.1~esm4
Available with Ubuntu Pro

Ubuntu 20.04 LTS
python3-tornado 6.0.3+really5.1.1-3ubuntu0.1~esm3
Available with Ubuntu Pro

Ubuntu 18.04 LTS
python-tornado 4.5.3-1ubuntu0.2+esm2
Available with Ubuntu Pro
python3-tornado 4.5.3-1ubuntu0.2+esm2
Available with Ubuntu Pro

Ubuntu 16.04 LTS
python-tornado 4.2.1-1ubuntu3.1+esm2
Available with Ubuntu Pro
python3-tornado 4.2.1-1ubuntu3.1+esm2
Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-7950-1
CVE-2025-67724, CVE-2025-67725, CVE-2025-67726

Package Information:
https://launchpad.net/ubuntu/+source/python-tornado/6.4.2-3ubuntu0.2
https://launchpad.net/ubuntu/+source/python-tornado/6.4.2-1ubuntu0.25.04.3
https://launchpad.net/ubuntu/+source/python-tornado/6.4.0-1ubuntu0.4

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