In Tornado before 6.5.5, cookie attribute injection could occur because the domain, path, and samesite arguments to .RequestHandler.set_cookie were not checked for crafted characters.

The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 25.10 host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8198-1 advisory.

    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)

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

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

The version of the Tornado Python library installed on the remote host is prior to 6.5.5. It is, therefore, affected by a cookie attribute injection vulnerability:

  - Cookie attribute injection could occur because the domain, path, and samesite arguments to     RequestHandler.set_cookie were not checked for crafted characters. In particular, semicolons     would be allowed, which could be used to inject attacker-controlled values for other cookie     attributes. (CVE-2026-35536)

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

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - In Tornado before 6.5.5, cookie attribute injection could occur because the domain, path, and samesite     arguments to .RequestHandler.set_cookie were not checked for crafted characters. (CVE-2026-35536)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
309910	Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 25.10 : Tornado vulnerabilities (USN-8198-1)	Nessus	Ubuntu Local Security Checks	high
307354	Python Library Tornado < 6.5.5 Cookie Attribute Injection	Nessus	Misc.	medium
304899	Linux Distros Unpatched Vulnerability : CVE-2026-35536	Nessus	Misc.	medium

Detections

Analytics

CVE-2026-35536

medium

Tenable Plugins

high

medium

medium