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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-8790-1)

medium Nessus Plugin ID 350305

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-8790-1 advisory.

 It was discovered that Expat could be made to allocate large amounts of memory when parsing a small crafted document. An attacker could possibly use this issue to cause Expat to consume resources, leading to a denial of service. This issue was only addressed in Ubuntu 24.04 LTS. (CVE-2025-59375)

 It was discovered that Expat incorrectly handled empty external parameter entity content. An attacker could possibly use this issue to cause Expat to crash, resulting in a denial of service. (CVE-2026-32776)

 It was discovered that Expat incorrectly handled certain DTD content. An attacker could possibly use this issue to cause Expat to enter an infinite loop, resulting in a denial of service. (CVE-2026-32777)

 It was discovered that Expat incorrectly handled memory when retrying after an earlier out-of-memory condition. An attacker could possibly use this issue to cause Expat to crash, resulting in a denial of service. (CVE-2026-32778)

 It was discovered that Expat performed attribute name collision checks inefficiently. An attacker could possibly use this issue to cause Expat to consume resources when processing a moderately sized crafted XML document, resulting in a denial of service.

 This issue was only addressed in Ubuntu 24.04 LTS and Ubuntu 26.04 LTS. (CVE-2026-45186)

 It was discovered that Expat used insufficient entropy, allowing hash flooding through a crafted XML document. An attacker could possibly use this issue to cause Expat to consume resources, leading to a denial of service.

 This issue was only addressed in Ubuntu 14.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS.
 (CVE-2026-41080)

 It was discovered that Expat did not track handler call depth for certain functions called from within handlers, leading to a use-after-free. An attacker could possibly use this issue to cause Expat to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2026-50219, CVE-2026-56412)

 It was discovered that Expat incorrectly handled certain values, leading to integer overflows. An attacker could possibly use this issue to cause Expat to crash, resulting in a denial of service. (CVE-2026-56403, CVE-2026-56404, CVE-2026-56405)

 It was discovered that Expat incorrectly handled certain values, leading to an integer overflow. An attacker could possibly use this issue to cause Expat to crash, resulting in a denial of service. This issue only affected Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS. (CVE-2026-56408)

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-8790-1

Plugin Details

Severity: Medium

ID: 350305

File Name: ubuntu_USN-8790-1.nasl

Version: 1.1

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: 5.7

Percentile: 96.25

CVSS v2

Risk Factor: Medium

Base Score: 4.6

Temporal Score: 3.6

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

CVSS Score Source: CVE-2026-56412

CVSS v3

Risk Factor: Medium

Base Score: 6.9

Temporal Score: 6.2

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

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

CVSS Score Source: CVE-2026-56405

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: 9/21/2026

Vulnerability Publication Date: 3/16/2026

Reference Information

CVE: CVE-2025-59375, CVE-2026-32776, CVE-2026-32777, CVE-2026-32778, CVE-2026-41080, CVE-2026-45186, CVE-2026-50219, CVE-2026-56403, CVE-2026-56404, CVE-2026-56405, CVE-2026-56408, CVE-2026-56412

IAVA: 2026-A-0407-S, 2026-A-0451, 2026-A-0650-S

USN: 8790-1