Detections
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Linux Distros Unpatched Vulnerability : CVE-2026-42923
medium Nessus Plugin ID 315757
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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.- NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability in the DNSSEC validator where the code path to consult the negative cache for DS records does not take into account the limit on NSEC3 hash calculations introduced in 1.19.1. This leads to degradation of service during the attack. An adversary that controls a DNSSEC signed zone can exploit this by signing NSEC3 records with acceptably high iterations for child delegations and querying a vulnerable Unbound. Unbound will keep performing the allowed hash calculations on the NSEC3 records and will not limit the work by the mitigation introduced in 1.19.1. As a side effect, a global lock for the negative cache will be held for the duration of the hashing, blocking other threads that need to consult the negative cache. Coordinated attacks could raise the vulnerability to denial of service. Unbound 1.25.1 contains a patch with a fix to bound the vulnerable code path with the existing limit for NSEC3 hash calculations. (CVE-2026-42923)
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-2026-42923
Plugin Details
Severity: Medium
ID: 315757
File Name: unpatched_CVE_2026_42923.nasl
Version: 1.6
Type: Local
Agent: unix
Family: Misc.
Published: 5/20/2026
Updated: 5/28/2026
Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Azure, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Nessus
Risk Information
VPR
Risk Factor: Low
Score: 2.2
CVSS v2
Risk Factor: Medium
Base Score: 5
Temporal Score: 4.3
Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:P
CVSS Score Source: CVE-2026-42923
CVSS v3
Risk Factor: Medium
Base Score: 5.3
Temporal Score: 4.9
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Temporal Vector: CVSS:3.0/E:U/RL:U/RC:C
CVSS v4
Risk Factor: Medium
Base Score: 6.9
Threat Score: 2.7
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:L/SC:N/SI:N/SA:N
Vulnerability Information
CPE: cpe:/o:debian:debian_linux:11.0, p-cpe:/a:centos:centos:python3-unbound, cpe:/o:canonical:ubuntu_linux:20.04:-:lts, p-cpe:/a:canonical:ubuntu_linux:unbound, cpe:/o:redhat:enterprise_linux:6, 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, cpe:/o:canonical:ubuntu_linux:18.04:-:lts, 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, cpe:/o:canonical:ubuntu_linux:14.04:-:lts, p-cpe:/a:debian:debian_linux:unbound, p-cpe:/a:centos:centos:unbound-utils, cpe:/o:centos:centos:7, p-cpe:/a:centos:centos:unbound-devel, p-cpe:/a:centos:centos:unbound-python, p-cpe:/a:centos:centos:unbound-dracut, p-cpe:/a:redhat:enterprise_linux:unbound-devel, p-cpe:/a:redhat:enterprise_linux:unbound-dracut, cpe:/o:canonical:ubuntu_linux:16.04:-:lts, cpe:/o:redhat:enterprise_linux:7, 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-2026-42923