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Linux Distros Unpatched Vulnerability : CVE-2026-56131

medium Nessus Plugin ID 321769

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Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

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

 - libexpat before 2.8.2 lacks handler call depth tracking for calls to XML_ResumeParser from within handlers in cases of a policy violation. Thus, a use-after-free can occur (similar to the CVE-2026-50219 situation). (CVE-2026-56131)

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

Solution

There is no known solution at this time.

See Also

https://access.redhat.com/security/cve/cve-2026-56131

https://security-tracker.debian.org/tracker/CVE-2026-56131

https://ubuntu.com/security/CVE-2026-56131

Plugin Details

Severity: Medium

ID: 321769

File Name: unpatched_CVE_2026_56131.nasl

Version: 1.6

Type: Local

Agent: unix

Family: Misc.

Published: 6/20/2026

Updated: 7/31/2026

Supported Sensors: Agentless 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: 2.8

Percentile: 22.52

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.4

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

CVSS Score Source: CVE-2026-56131

CVSS v3

Risk Factor: Medium

Base Score: 4.9

Temporal Score: 4.5

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

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

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:25.10, cpe:/o:canonical:ubuntu_linux:26.04:-:lts, cpe:/o:centos:centos:8, cpe:/o:debian:debian_linux:11.0, cpe:/o:debian:debian_linux:12.0, cpe:/o:redhat:enterprise_linux:10, cpe:/o:redhat:enterprise_linux:8, cpe:/o:redhat:enterprise_linux:9, p-cpe:/a:canonical:ubuntu_linux:ayttm, p-cpe:/a:canonical:ubuntu_linux:cableswig, p-cpe:/a:canonical:ubuntu_linux:cadaver, p-cpe:/a:canonical:ubuntu_linux:coin3, p-cpe:/a:canonical:ubuntu_linux:expat, p-cpe:/a:canonical:ubuntu_linux:gdcm, p-cpe:/a:canonical:ubuntu_linux:insighttoolkit4, p-cpe:/a:canonical:ubuntu_linux:libxmltok, p-cpe:/a:canonical:ubuntu_linux:matanza, p-cpe:/a:canonical:ubuntu_linux:smart, p-cpe:/a:canonical:ubuntu_linux:swish-e, p-cpe:/a:canonical:ubuntu_linux:tdom, p-cpe:/a:canonical:ubuntu_linux:vnc4, p-cpe:/a:canonical:ubuntu_linux:vtk, p-cpe:/a:canonical:ubuntu_linux:wbxml2, p-cpe:/a:canonical:ubuntu_linux:xmlrpc-c, p-cpe:/a:centos:centos:expat-devel, p-cpe:/a:centos:centos:expat, p-cpe:/a:centos:centos:firefox-x11, p-cpe:/a:centos:centos:firefox, p-cpe:/a:centos:centos:mingw-expat, p-cpe:/a:centos:centos:mingw32-expat, p-cpe:/a:centos:centos:mingw64-expat, p-cpe:/a:centos:centos:thunderbird, p-cpe:/a:centos:centos:xmlrpc-c-c%2b%2b, p-cpe:/a:centos:centos:xmlrpc-c-client, p-cpe:/a:centos:centos:xmlrpc-c-client%2b%2b, p-cpe:/a:centos:centos:xmlrpc-c-devel, p-cpe:/a:centos:centos:xmlrpc-c, p-cpe:/a:debian:debian_linux:expat, p-cpe:/a:redhat:enterprise_linux:expat-devel, p-cpe:/a:redhat:enterprise_linux:expat, p-cpe:/a:redhat:enterprise_linux:firefox-x11, p-cpe:/a:redhat:enterprise_linux:firefox, p-cpe:/a:redhat:enterprise_linux:mingw-expat, p-cpe:/a:redhat:enterprise_linux:mingw32-expat, p-cpe:/a:redhat:enterprise_linux:mingw64-expat, p-cpe:/a:redhat:enterprise_linux:thunderbird, p-cpe:/a:redhat:enterprise_linux:xmlrpc-c-c%2b%2b, p-cpe:/a:redhat:enterprise_linux:xmlrpc-c-client, p-cpe:/a:redhat:enterprise_linux:xmlrpc-c-client%2b%2b, p-cpe:/a:redhat:enterprise_linux:xmlrpc-c-devel, p-cpe:/a:redhat:enterprise_linux:xmlrpc-c

Required KB Items: Host/cpu, Host/local_checks_enabled, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 6/19/2026

Reference Information

CVE: CVE-2026-56131