Amazon Linux 2 : libxml2 (ALAS-2026-3940)

high Nessus Plugin ID 351063

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Synopsis

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

Description

The version of libxml2 installed on the remote host is prior to 2.9.1-6. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3940 advisory.

A flaw was found in libxml2 with Python bindings enabled. A remote attacker could exploit this vulnerability by providing a specially crafted XML document containing a Document Type Definition (DTD) with enumerated attribute values. This triggers a double-free error in the SAX attributeDecl callback handler, where a string is freed twice. This flaw can lead to a denial of service (DoS) due to a reproducible crash in Python applications using the libxml2 SAX bindings. (CVE-2026-74860)

In libxml2 before 2.15.4, xmlFAParsePosCharGroup has an out-of-bounds read, aka an out-of-bounds read in the NXT macro in xmlregexp. (CVE-2026-86137)

In libxml2 before 2.15.4, xmlDictAddQString in dict.c has an integer overflow and resultant heap-based buffer overflow. (CVE-2026-86138)

In libxml2 before 2.15.4, xmlSnprintfElements in valid.c has a strcat stack-based buffer overflow.
(CVE-2026-86140)

In libxml2 before 2.15.4, there is a heap-based buffer overflow in xmlXPtrEvalXPtrPart because of xmlXPtrEval xpointer length saturation. (CVE-2026-86142)

In xmlIO in libxml2 before 2.15.4, an inconsistency in xmlOutputWriteCallback and xmlBufUse causes negative lengths to reach write callbacks, aka a lack of a check for integer overflow before calling writecallback. This has security relevance for many types of uses of that length value within a callback.
(CVE-2026-86143)

In xinclude in libxml2 before 2.15.4, xmlXIncludeProcess and xmlXIncludeProcessTree do not propagate parseFlags. This has security relevance for, for example, the XML_PARSE_NONET flag, if (without it) a custom resource loader accesses the internet and triggers XML external entity injection, SSRF, or a denial of service (e.g., for an attacker-controlled internet resource that is intentionally slow).
(CVE-2026-86144)

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 libxml2' or or 'yum update --advisory ALAS2-2026-3940' to update your system.

Plugin Details

Severity: High

ID: 351063

File Name: al2_ALAS-2026-3940.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 9/29/2026

Updated: 9/29/2026

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: 6.9

Percentile: 96.5

CVSS v2

Risk Factor: Medium

Base Score: 6.8

Temporal Score: 5.3

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

CVSS Score Source: CVE-2026-86144

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 7

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:P/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:amazon:linux:2, p-cpe:/a:amazon:linux:libxml2-debuginfo, p-cpe:/a:amazon:linux:libxml2-devel, p-cpe:/a:amazon:linux:libxml2-python, p-cpe:/a:amazon:linux:libxml2-static, p-cpe:/a:amazon:linux:libxml2

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

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 9/28/2026

Vulnerability Publication Date: 9/5/2026

Reference Information

CVE: CVE-2026-74860, CVE-2026-86137, CVE-2026-86138, CVE-2026-86140, CVE-2026-86142, CVE-2026-86143, CVE-2026-86144

IAVA: 2026-A-0980

Detections

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