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Linux Distros Unpatched Vulnerability : CVE-2026-76957

high Nessus Plugin ID 338296

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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 2.8.4 lacks handler call depth tracking with custom encoding callbacks. Thus, a use-after- free can occur. NOTE: this is similar to CVE-2026-50219, CVE-2026-56131 and CVE-2026-56412.
 (CVE-2026-76957)

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-2026-76957

https://security-tracker.debian.org/tracker/CVE-2026-76957

https://ubuntu.com/security/CVE-2026-76957

Plugin Details

Severity: High

ID: 338296

File Name: unpatched_CVE_2026_76957.nasl

Version: 1.12

Type: Local

Agent: unix

Family: Misc.

Published: 8/20/2026

Updated: 9/10/2026

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Azure, Frictionless Assessment Agent, Nessus Agent, Agentless 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: 5.8

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: 7.1

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: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:26.04:-:lts, cpe:/o:centos:centos:7, cpe:/o:centos:centos:8, cpe:/o:debian:debian_linux:13.0, cpe:/o:redhat:enterprise_linux:10, cpe:/o:redhat:enterprise_linux:6, cpe:/o:redhat:enterprise_linux:7, 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:compat-expat1, p-cpe:/a:centos:centos:expat-devel, p-cpe:/a:centos:centos:expat-static, p-cpe:/a:centos:centos:expat, 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:compat-expat1, p-cpe:/a:redhat:enterprise_linux:expat-devel, p-cpe:/a:redhat:enterprise_linux:expat-static, p-cpe:/a:redhat:enterprise_linux:expat, 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/local_checks_enabled, Host/cpu, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 8/20/2026

Reference Information

CVE: CVE-2026-76957