Amazon Linux 2 : perl (ALAS-2026-3997)

critical Nessus Plugin ID 365203

Synopsis

The remote Amazon Linux 2 host is missing a security update.

Description

The version of perl installed on the remote host is prior to 5.16.3-299. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3997 advisory.

Perl versions through 5.43.9 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)

Perl versions through 5.43.10 have an integer overflow in S_measure_struct leading to an out-of-bounds heap read in pack and unpack.

S_measure_struct adds each item's size times its repeat count to a running total with no overflow check, so a large repeat count in a pack or unpack template wraps the signed SSize_t total negative. The @, X, and x position codes then guard their moves with a signed length comparison that passes when the length is negative, advancing the buffer pointer out of bounds.

A template derived from untrusted input can read heap memory past the buffer and return it to the caller.
(CVE-2026-57432)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Run 'yum update perl' or or 'yum update --advisory ALAS2-2026-3997' to update your system.

Plugin Details

Severity: Critical

ID: 365203

File Name: al2_ALAS-2026-3997.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 10/12/2026

Updated: 10/12/2026

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Continuous 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: 7

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: 7.9

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:O/RC:C

Vulnerability Information

CPE: cpe:/o:amazon:linux:2, p-cpe:/a:amazon:linux:perl-core, p-cpe:/a:amazon:linux:perl-cpan, p-cpe:/a:amazon:linux:perl-debuginfo, p-cpe:/a:amazon:linux:perl-devel, p-cpe:/a:amazon:linux:perl-extutils-cbuilder, p-cpe:/a:amazon:linux:perl-extutils-embed, p-cpe:/a:amazon:linux:perl-extutils-install, p-cpe:/a:amazon:linux:perl-io-zlib, p-cpe:/a:amazon:linux:perl-libs, p-cpe:/a:amazon:linux:perl-locale-maketext-simple, p-cpe:/a:amazon:linux:perl-macros, p-cpe:/a:amazon:linux:perl-module-corelist, p-cpe:/a:amazon:linux:perl-module-loaded, p-cpe:/a:amazon:linux:perl-object-accessor, p-cpe:/a:amazon:linux:perl-package-constants, p-cpe:/a:amazon:linux:perl-pod-escapes, p-cpe:/a:amazon:linux:perl-tests, p-cpe:/a:amazon:linux:perl-time-piece, p-cpe:/a:amazon:linux:perl

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 10/12/2026

Vulnerability Publication Date: 7/13/2026

Reference Information

CVE: CVE-2026-13221, CVE-2026-57432

IAVA: 2026-A-0696-S

Detections

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