Amazon Linux 2 : 389-ds-base (ALAS-2026-3957)

high Nessus Plugin ID 351082

Synopsis

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

Description

The version of 389-ds-base installed on the remote host is prior to 1.3.10.2-17. It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2-2026-3957 advisory.

A heap buffer overflow flaw was found in the SASL I/O layer of 389 Directory Server (389-ds-base). In sasl_io_start_packet(), the wrapped-record length read from the wire is validated only against an upper bound. A small wire length (0, 1, or 2) produces an encrypted_buffer_count below the already-consumed encrypted_buffer_offset, causing an unsigned subtraction underflow in sasl_io_read_packet(). PR_Recv is then requested to read approximately 4 GiB into a 1024-byte heap buffer, resulting in a heap buffer overflow with attacker-controlled content. After a successful SASL bind with integrity protection (SSF > 0), a remote authenticated attacker can cause a denial of service or potentially achieve remote code execution. This flaw is distinct from CVE-2026-11774, whose fix only guards against upper-bound overflow.
(CVE-2026-18355)

A flaw was found in 389 Directory Server. A missing NULL pointer check in the paged results handling of op_shared_search allows an unauthenticated remote attacker to crash the LDAP server by sending a crafted sequence of search requests using the USE_ONE_BACKEND control, resulting in denial of service.
(CVE-2026-18453)

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 389-ds-base' or or 'yum update --advisory ALAS2-2026-3957' to update your system.

Plugin Details

Severity: High

ID: 351082

File Name: al2_ALAS-2026-3957.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 9/29/2026

Updated: 9/29/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.15

CVSS v2

Risk Factor: High

Base Score: 7.1

Temporal Score: 5.3

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

CVSS Score Source: CVE-2026-18355

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

Vector: CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/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:389-ds-base-debuginfo, p-cpe:/a:amazon:linux:389-ds-base-devel, p-cpe:/a:amazon:linux:389-ds-base-libs, p-cpe:/a:amazon:linux:389-ds-base-snmp, p-cpe:/a:amazon:linux:389-ds-base

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

Exploit Ease: No known exploits are available

Patch Publication Date: 9/28/2026

Vulnerability Publication Date: 9/7/2026

Reference Information

CVE: CVE-2026-18355, CVE-2026-18453

Detections

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