Detections
Analytics

Amazon Linux 2 : libreswan (ALAS-2026-4021)

high Nessus Plugin ID 371784

Synopsis

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

Description

The version of libreswan installed on the remote host is prior to 3.25-4.8. It is, therefore, affected by a vulnerability as referenced in the ALAS2-2026-4021 advisory.

 A null pointer dereference flaw was found in Libreswan's PKCS#7 certificate payload handling. When processing a crafted IKEv2 IKE_AUTH packet containing a PKCS#7 bundle with a certificate revocation list but no certificates, Libreswan may dereference a null pointer, causing the pluto daemon to crash and restart. A remote, unauthenticated attacker could repeatedly trigger this flaw to cause a denial of service. (CVE-2026-77207)

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

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

Solution

Run 'yum update libreswan' or or 'yum update --advisory ALAS2-2026-4021' to update your system.

See Also

https://alas.aws.amazon.com//AL2/ALAS2-2026-4021.html

https://alas.aws.amazon.com/faqs.html

https://explore.alas.aws.amazon.com/CVE-2026-77207.html

Plugin Details

Severity: High

ID: 371784

File Name: al2_ALAS-2026-4021.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 10/24/2026

Updated: 10/24/2026

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: Low

Score: 3

Percentile: 23.71

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

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

CVSS Score Source: CVE-2026-77207

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

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:O/RC:C

Vulnerability Information

CPE: cpe:/o:amazon:linux:2, p-cpe:/a:amazon:linux:libreswan-debuginfo, p-cpe:/a:amazon:linux:libreswan

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

Exploit Ease: No known exploits are available

Patch Publication Date: 10/24/2026

Vulnerability Publication Date: 10/13/2026

Reference Information

CVE: CVE-2026-77207