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Linux Distros Unpatched Vulnerability : CVE-2026-13221

critical Nessus Plugin ID 326561

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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.

 - Perl versions before 5.40.5-RC1, from 5.41.0 before 5.42.3-RC1, from 5.43.0 before 5.43.10 produce silently incorrect regular expression matches when an alternation of more than 65535 fixed string branches is compiled into a trie in Perl_study_chunk. When such branches are combined into a trie, the delta between the first branch and the shared tail is stored in a 16-bit field. A branch count above 65535 overflows the field, and the trie's match decision table is truncated with no warning or error. A pattern of this shape produces false positive matches (matching strings it should not) and false negative matches (failing to match strings it should). When such a pattern gates an access or filtering decision, the result is wrong. (CVE-2026-13221)

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-2026-13221

https://security-tracker.debian.org/tracker/CVE-2026-13221

Plugin Details

Severity: Critical

ID: 326561

File Name: unpatched_CVE_2026_13221.nasl

Version: 1.14

Type: Local

Agent: unix

Family: Misc.

Published: 7/13/2026

Updated: 9/14/2026

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: 6.3

Percentile: 96.31

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 8

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

CVSS Score Source: CVE-2026-13221

CVSS v3

Risk Factor: Critical

Base Score: 9.1

Temporal Score: 8.3

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

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

Vulnerability Information

CPE: cpe:/o:centos:centos:7, cpe:/o:debian:debian_linux:12.0, cpe:/o:redhat:enterprise_linux:6, cpe:/o:redhat:enterprise_linux:7, p-cpe:/a:centos:centos:perl-archive-extract, p-cpe:/a:centos:centos:perl-archive-tar, p-cpe:/a:centos:centos:perl-cgi, p-cpe:/a:centos:centos:perl-compress-raw-bzip2, p-cpe:/a:centos:centos:perl-compress-raw-zlib, p-cpe:/a:centos:centos:perl-compress-zlib, p-cpe:/a:centos:centos:perl-core, p-cpe:/a:centos:centos:perl-cpan, p-cpe:/a:centos:centos:perl-cpanplus, p-cpe:/a:centos:centos:perl-devel, p-cpe:/a:centos:centos:perl-digest-sha, p-cpe:/a:centos:centos:perl-extutils-cbuilder, p-cpe:/a:centos:centos:perl-extutils-embed, p-cpe:/a:centos:centos:perl-extutils-install, p-cpe:/a:centos:centos:perl-extutils-makemaker, p-cpe:/a:centos:centos:perl-extutils-parsexs, p-cpe:/a:centos:centos:perl-file-fetch, p-cpe:/a:centos:centos:perl-io-compress-base, p-cpe:/a:centos:centos:perl-io-compress-bzip2, p-cpe:/a:centos:centos:perl-io-compress-zlib, p-cpe:/a:centos:centos:perl-io-zlib, p-cpe:/a:centos:centos:perl-ipc-cmd, p-cpe:/a:centos:centos:perl-libs, p-cpe:/a:centos:centos:perl-locale-maketext-simple, p-cpe:/a:centos:centos:perl-log-message-simple, p-cpe:/a:centos:centos:perl-log-message, p-cpe:/a:centos:centos:perl-macros, p-cpe:/a:centos:centos:perl-module-build, p-cpe:/a:centos:centos:perl-module-corelist, p-cpe:/a:centos:centos:perl-module-load-conditional, p-cpe:/a:centos:centos:perl-module-load, p-cpe:/a:centos:centos:perl-module-loaded, p-cpe:/a:centos:centos:perl-module-pluggable, p-cpe:/a:centos:centos:perl-object-accessor, p-cpe:/a:centos:centos:perl-package-constants, p-cpe:/a:centos:centos:perl-params-check, p-cpe:/a:centos:centos:perl-parent, p-cpe:/a:centos:centos:perl-parse-cpan-meta, p-cpe:/a:centos:centos:perl-pod-escapes, p-cpe:/a:centos:centos:perl-pod-simple, p-cpe:/a:centos:centos:perl-suidperl, p-cpe:/a:centos:centos:perl-term-ui, p-cpe:/a:centos:centos:perl-test-harness, p-cpe:/a:centos:centos:perl-test-simple, p-cpe:/a:centos:centos:perl-tests, p-cpe:/a:centos:centos:perl-time-hires, p-cpe:/a:centos:centos:perl-time-piece, p-cpe:/a:centos:centos:perl-version, p-cpe:/a:centos:centos:perl, p-cpe:/a:debian:debian_linux:perl, p-cpe:/a:redhat:enterprise_linux:perl-archive-extract, p-cpe:/a:redhat:enterprise_linux:perl-archive-tar, p-cpe:/a:redhat:enterprise_linux:perl-cgi, p-cpe:/a:redhat:enterprise_linux:perl-compress-raw-bzip2, p-cpe:/a:redhat:enterprise_linux:perl-compress-raw-zlib, p-cpe:/a:redhat:enterprise_linux:perl-compress-zlib, p-cpe:/a:redhat:enterprise_linux:perl-core, p-cpe:/a:redhat:enterprise_linux:perl-cpan, p-cpe:/a:redhat:enterprise_linux:perl-cpanplus, p-cpe:/a:redhat:enterprise_linux:perl-devel, p-cpe:/a:redhat:enterprise_linux:perl-digest-sha, p-cpe:/a:redhat:enterprise_linux:perl-extutils-cbuilder, p-cpe:/a:redhat:enterprise_linux:perl-extutils-embed, p-cpe:/a:redhat:enterprise_linux:perl-extutils-install, p-cpe:/a:redhat:enterprise_linux:perl-extutils-makemaker, p-cpe:/a:redhat:enterprise_linux:perl-extutils-parsexs, p-cpe:/a:redhat:enterprise_linux:perl-file-fetch, p-cpe:/a:redhat:enterprise_linux:perl-io-compress-base, p-cpe:/a:redhat:enterprise_linux:perl-io-compress-bzip2, p-cpe:/a:redhat:enterprise_linux:perl-io-compress-zlib, p-cpe:/a:redhat:enterprise_linux:perl-io-zlib, p-cpe:/a:redhat:enterprise_linux:perl-ipc-cmd, p-cpe:/a:redhat:enterprise_linux:perl-libs, p-cpe:/a:redhat:enterprise_linux:perl-locale-maketext-simple, p-cpe:/a:redhat:enterprise_linux:perl-log-message-simple, p-cpe:/a:redhat:enterprise_linux:perl-log-message, p-cpe:/a:redhat:enterprise_linux:perl-macros, p-cpe:/a:redhat:enterprise_linux:perl-module-build, p-cpe:/a:redhat:enterprise_linux:perl-module-corelist, p-cpe:/a:redhat:enterprise_linux:perl-module-load-conditional, p-cpe:/a:redhat:enterprise_linux:perl-module-load, p-cpe:/a:redhat:enterprise_linux:perl-module-loaded, p-cpe:/a:redhat:enterprise_linux:perl-module-pluggable, p-cpe:/a:redhat:enterprise_linux:perl-object-accessor, p-cpe:/a:redhat:enterprise_linux:perl-package-constants, p-cpe:/a:redhat:enterprise_linux:perl-params-check, p-cpe:/a:redhat:enterprise_linux:perl-parent, p-cpe:/a:redhat:enterprise_linux:perl-parse-cpan-meta, p-cpe:/a:redhat:enterprise_linux:perl-pod-escapes, p-cpe:/a:redhat:enterprise_linux:perl-pod-simple, p-cpe:/a:redhat:enterprise_linux:perl-suidperl, p-cpe:/a:redhat:enterprise_linux:perl-term-ui, p-cpe:/a:redhat:enterprise_linux:perl-test-harness, p-cpe:/a:redhat:enterprise_linux:perl-test-simple, p-cpe:/a:redhat:enterprise_linux:perl-tests, p-cpe:/a:redhat:enterprise_linux:perl-time-hires, p-cpe:/a:redhat:enterprise_linux:perl-time-piece, p-cpe:/a:redhat:enterprise_linux:perl-version, p-cpe:/a:redhat:enterprise_linux:perl

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: 7/13/2026

Reference Information

CVE: CVE-2026-13221