Detections
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Linux Distros Unpatched Vulnerability : CVE-2026-42959

high Nessus Plugin ID 315768

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.

 - NLnet Labs Unbound up to and including version 1.25.0 has a denial of service vulnerability in the DNSSEC validator that can lead to a crash given malicious upstream replies. When Unbound constructs chase-reply messages for validation, the code uses the wrong counter to calculate write offsets for ADDITIONAL section rrsets. DNAME duplication could increase the ANSWER section count and authority filtering could decrease the AUTHORITY section count and create an uninitialized array slot. Combining these two, the validator later dereferences this uninitialized pointer, causing an immediate process crash. An adversary controlling a DNSSEC-signed domain can trigger this bug with a single query by configuring a DNAME chain with unsigned CNAMEs and a response containing unsigned AUTHORITY records alongside signed ADDITIONAL glue records. Unbound 1.25.1 contains a patch with a fix to use the proper counters to calculate the write offsets. (CVE-2026-42959)

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-2026-42959

https://security-tracker.debian.org/tracker/CVE-2026-42959

Plugin Details

Severity: High

ID: 315768

File Name: unpatched_CVE_2026_42959.nasl

Version: 1.2

Type: Local

Agent: unix

Family: Misc.

Published: 5/20/2026

Updated: 5/21/2026

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

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.6

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

CVSS Score Source: CVE-2026-42959

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.9

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

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

CVSS v4

Risk Factor: High

Base Score: 8.7

Threat Score: 6.6

Threat Vector: CVSS:4.0/E:U

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

Vulnerability Information

CPE: cpe:/o:debian:debian_linux:11.0, p-cpe:/a:centos:centos:python3-unbound, p-cpe:/a:redhat:enterprise_linux:unbound-anchor, p-cpe:/a:redhat:enterprise_linux:unbound, cpe:/o:debian:debian_linux:12.0, p-cpe:/a:centos:centos:unbound-libs, p-cpe:/a:redhat:enterprise_linux:unbound-libs, p-cpe:/a:centos:centos:unbound, cpe:/o:redhat:enterprise_linux:9, p-cpe:/a:centos:centos:unbound-anchor, p-cpe:/a:redhat:enterprise_linux:unbound-python, cpe:/o:centos:centos:8, p-cpe:/a:redhat:enterprise_linux:python3-unbound, cpe:/o:redhat:enterprise_linux:8, cpe:/o:redhat:enterprise_linux:10, cpe:/o:debian:debian_linux:13.0, p-cpe:/a:debian:debian_linux:unbound, p-cpe:/a:centos:centos:unbound-utils, cpe:/o:centos:centos:7, p-cpe:/a:redhat:enterprise_linux:unbound-dracut, cpe:/o:redhat:enterprise_linux:7, p-cpe:/a:centos:centos:unbound-devel, p-cpe:/a:centos:centos:unbound-python, p-cpe:/a:centos:centos:unbound-dracut, cpe:/o:debian:debian_linux:14.0, p-cpe:/a:redhat:enterprise_linux:unbound-devel, p-cpe:/a:redhat:enterprise_linux:unbound-utils

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: 5/20/2026

Reference Information

CVE: CVE-2026-42959