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Ubuntu 16.04 LTS / 18.04 LTS : Tomcat vulnerabilities (USN-8551-1)

critical Nessus Plugin ID 327338

Synopsis

The remote Ubuntu host is missing one or more security updates.

Description

The remote Ubuntu 16.04 LTS / 18.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8551-1 advisory.

 It was discovered that Tomcat incorrectly handled authorization when multiple method constraints defined the same HTTP method. A remote attacker could possibly use this issue to bypass authorization restrictions. (CVE-2026-43515)

 It was discovered that the Tomcat number guess example application did not properly sanitize user-supplied input. An attacker could possibly use this issue to inject malicious scripts, resulting in cross-site scripting. (CVE-2026-50229)

 It was discovered that Tomcat incorrectly evaluated rewrite valve conditions in certain configurations. An attacker could possibly use this issue to bypass rewrite rules, resulting in unauthorized access.
 (CVE-2026-53404)

 It was discovered that Tomcat incorrectly omitted certain authorization information when logging the effective web.xml configuration. An attacker could possibly use this issue to hide authorization constraints, resulting in reduced auditability. (CVE-2026-55276)

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.

Solution

Update the affected packages.

See Also

https://ubuntu.com/security/notices/USN-8551-1

Plugin Details

Severity: Critical

ID: 327338

File Name: ubuntu_USN-8551-1.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 7/16/2026

Updated: 7/16/2026

Supported Sensors: Agentless Assessment, Continuous Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Frictionless Assessment Azure, Nessus Agent, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.3

Percentile: 53.7

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 7.4

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:N

CVSS Score Source: CVE-2026-55276

CVSS v3

Risk Factor: Critical

Base Score: 9.1

Temporal Score: 8.2

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:16.04:-:lts, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:tomcat8-admin, p-cpe:/a:canonical:ubuntu_linux:tomcat8-common, p-cpe:/a:canonical:ubuntu_linux:libtomcat8-java, p-cpe:/a:canonical:ubuntu_linux:tomcat8-examples, p-cpe:/a:canonical:ubuntu_linux:libtomcat8-embed-java, p-cpe:/a:canonical:ubuntu_linux:tomcat8-user, p-cpe:/a:canonical:ubuntu_linux:libservlet3.1-java, p-cpe:/a:canonical:ubuntu_linux:tomcat8

Required KB Items: Host/cpu, Host/Ubuntu, Host/Ubuntu/release, Host/Debian/dpkg-l

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 7/15/2026

Vulnerability Publication Date: 5/5/2026

Reference Information

CVE: CVE-2026-43515, CVE-2026-50229, CVE-2026-53404, CVE-2026-55276

IAVA: 2026-A-0475, 2026-A-0642

USN: 8551-1