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Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS : Expat vulnerabilities (USN-8813-1)

high Nessus Plugin ID 350173

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Synopsis

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

Description

The remote Ubuntu 14.04 LTS / 16.04 LTS / 18.04 LTS / 20.04 LTS / 22.04 LTS / 24.04 LTS / 26.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-8813-1 advisory.

 It was discovered that Expat did not correctly handle certain integer arithmetic. An attacker could possibly use this issue to cause a denial of service.

 (CVE-2026-56406, CVE-2026-56407, CVE-2026-56409, CVE-2026-56410, CVE-2026-56411)

 It was discovered that Expat did not correctly track handler call depth. An attacker could possibly use this issue to cause Expat to crash or execute arbitrary code. (CVE-2026-56131)

 It was discovered that Expat did not correctly handle certain memory operations. An attacker could possibly use this issue to cause Expat to crash or execute arbitrary code. (CVE-2026-56132)

 It was discovered that Expat did not correctly handle certain Unicode characters. An attacker could possibly use this issue to cause Expat to use excessive resources, leading to a denial of service.
 (CVE-2026-72522)

 It was discovered that Expat did not correctly process certain XML attributes. A remote attacker could possibly use this issue to cause Expat to use excessive resources, leading to a denial of service.
 (CVE-2026-66046)

 It was discovered that Expat did not correctly handle certain external entities. An attacker could possibly use this issue to cause Expat to crash or execute arbitrary code. (CVE-2026-76641)

 It was discovered that Expat did not correctly track handler call depth with custom encodings. An attacker could possibly use this issue to cause Expat to crash or execute arbitrary code. (CVE-2026-76957)

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 expat, lib64expat1 and / or libexpat1 packages.

See Also

https://ubuntu.com/security/notices/USN-8813-1

Plugin Details

Severity: High

ID: 350173

File Name: ubuntu_USN-8813-1.nasl

Version: 1.2

Type: Local

Agent: unix

Published: 9/25/2026

Updated: 9/25/2026

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

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.15

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5.3

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

CVSS Score Source: CVE-2026-76957

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 7

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

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

CVSS v4

Risk Factor: High

Base Score: 8.7

Threat Score: 7.7

Threat Vector: CVSS:4.0/E:P

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS Score Source: CVE-2026-76641

Vulnerability Information

CPE: cpe:/o:canonical:ubuntu_linux:14.04:-:lts, cpe:/o:canonical:ubuntu_linux:16.04:-:lts, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, cpe:/o:canonical:ubuntu_linux:20.04:-:lts, cpe:/o:canonical:ubuntu_linux:22.04:-:lts, cpe:/o:canonical:ubuntu_linux:24.04:-:lts, cpe:/o:canonical:ubuntu_linux:26.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:expat, p-cpe:/a:canonical:ubuntu_linux:lib64expat1, p-cpe:/a:canonical:ubuntu_linux:libexpat1

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

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 9/24/2026

Vulnerability Publication Date: 6/19/2026

Reference Information

CVE: CVE-2026-56131, CVE-2026-56132, CVE-2026-56406, CVE-2026-56407, CVE-2026-56409, CVE-2026-56410, CVE-2026-56411, CVE-2026-66046, CVE-2026-72522, CVE-2026-76641, CVE-2026-76957

IAVA: 2026-A-0650-S, 2026-A-0899-S, 2026-A-0925-S

USN: 8813-1