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[USN-8198-1] Tornado vulnerabilities

Posted on 23 April 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8198-1
April 22, 2026

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

- Ubuntu 25.10
- 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 parsing of large
multipart request bodies. An attacker could possibly use this issue to
cause a denial of service. (CVE-2026-31958)

It was discovered that Tornado did not properly validate characters in
cookie values. An attacker could possibly use this issue to inject
arbitrary cookie attributes. (CVE-2026-35536)

Update instructions:

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

Ubuntu 25.10
python3-tornado 6.4.2-3ubuntu0.3

Ubuntu 24.04 LTS
python3-tornado 6.4.0-1ubuntu0.5

Ubuntu 22.04 LTS
python3-tornado 6.1.0-3ubuntu0.1~esm5
Available with Ubuntu Pro

Ubuntu 20.04 LTS
python3-tornado 6.0.3+really5.1.1-3ubuntu0.1~esm5
Available with Ubuntu Pro

Ubuntu 18.04 LTS
python-tornado 4.5.3-1ubuntu0.2+esm3
Available with Ubuntu Pro
python3-tornado 4.5.3-1ubuntu0.2+esm3
Available with Ubuntu Pro

Ubuntu 16.04 LTS
python-tornado 4.2.1-1ubuntu3.1+esm3
Available with Ubuntu Pro
python3-tornado 4.2.1-1ubuntu3.1+esm3
Available with Ubuntu Pro

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

References:
https://ubuntu.com/security/notices/USN-8198-1
CVE-2026-31958, CVE-2026-35536

Package Information:
https://launchpad.net/ubuntu/+source/python-tornado/6.4.2-3ubuntu0.3
https://launchpad.net/ubuntu/+source/python-tornado/6.4.0-1ubuntu0.5

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