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Ubuntu 16.04 LTS : Expat vulnerability (USN-8520-1)

high Nessus Plugin ID 326308

Synopsis

The remote Ubuntu host is missing a security update.

Description

The remote Ubuntu 16.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-8520-1 advisory.

 It was discovered that Expat used insufficient entropy when generating hash salt values for its internal hash table. An attacker could use this to craft an XML document that triggers hash flooding, leading to a denial of service.

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

Note that Nessus has not tested for this issue 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-8520-1

Plugin Details

Severity: High

ID: 326308

File Name: ubuntu_USN-8520-1.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 7/10/2026

Updated: 7/10/2026

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: Low

Score: 3

Percentile: 23.75

CVSS v2

Risk Factor: Low

Base Score: 1.2

Temporal Score: 0.9

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

CVSS Score Source: CVE-2026-41080

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

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

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

Vulnerability Information

CPE: p-cpe:/a:canonical:ubuntu_linux:libexpat1, p-cpe:/a:canonical:ubuntu_linux:expat, p-cpe:/a:canonical:ubuntu_linux:lib64expat1, cpe:/o:canonical:ubuntu_linux:16.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:libexpat1-dev, p-cpe:/a:canonical:ubuntu_linux:lib64expat1-dev

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

Exploit Ease: No known exploits are available

Patch Publication Date: 7/9/2026

Vulnerability Publication Date: 4/16/2026

Reference Information

CVE: CVE-2026-41080

IAVA: 2026-A-0407-S

USN: 8520-1