Ubuntu Security Notices USN-8198-1 USN-8198-1: Tornado vulnerabilities Publication date 22 April 2026 Overview Several security issues were fixed in Tornado. Releases 25.10 24.04 LTS 22.04 LTS 20.04 LTS 18.04 LTS 16.04 LTS Open side navigation Close side navigation Packages Details Update instructions References Packages 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 ) 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 In general, a standard system update will make all the necessary changes. Learn more about how to get the fixes. The problem can be corrected by updating your system to the following package versions: Ubuntu Release Package Version 25.10 questing python3-tornado – 6.4.2-3ubuntu0.3 24.04 LTS noble python3-tornado – 6.4.0-1ubuntu0.5 22.04 LTS jammy python3-tornado – 6.1.0-3ubuntu0.1~esm5 Ubuntu Pro Fix available with Ubuntu Pro via ESM Apps. A community fix might become publicly available in the future. 20.04 LTS focal python3-tornado – 6.0.3+really5.1.1-3ubuntu0.1~esm5 Ubuntu Pro Fix available with Ubuntu Pro via ESM Apps. A community fix might become publicly available in the future. 18.04 LTS bionic python-tornado – 4.5.3-1ubuntu0.2+esm3 Ubuntu Pro Fix available with Ubuntu Pro via ESM Apps. A community fix might become publicly available in the future. python3-tornado – 4.5.3-1ubuntu0.2+esm3 Ubuntu Pro Fix available with Ubuntu Pro via ESM Apps. A community fix might become publicly available in the future. 16.04 LTS xenial python-tornado – 4.2.1-1ubuntu3.1+esm3 Ubuntu Pro Fix available with Ubuntu Pro . python3-tornado – 4.2.1-1ubuntu3.1+esm3 Ubuntu Pro Fix available with Ubuntu Pro . Reduce your security exposure Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines. Get Ubuntu Pro References CVE-2026-35536 CVE-2026-31958 CVE-2026-35536 CVE-2026-31958