Amazon Linux 2 : krb5, --advisory ALAS2-2026-3798 (ALAS-2026-3798)

medium Nessus Plugin ID 328841

Synopsis

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

Description

It is, therefore, affected by a vulnerability as referenced in the ALAS2-2026-3798 advisory.

An integer underflow vulnerability was found in MIT krb5 in the berval2tl_data() function in plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c. The function performs an unsigned subtraction (bv_len - 2) without a prior bounds check. When bv_len is 0 or 1, the subtraction wraps to a large value which is then truncated to uint16_t, yielding 0xFFFE (65534) or 0xFFFF (65535). The subsequent malloc succeeds and memcpy reads up to 65534 bytes from a 0-1 byte buffer, resulting in a heap out-of-bounds read.The attack vector involves a malicious or compromised LDAP KDB backend returning a krbExtraData attribute with bv_len < 2, triggering the underflow when the KDC or kadmind reads principal data. (CVE-2026-11850)

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 krb5' or or 'yum update --advisory ALAS2-2026-3798' to update your system.

Plugin Details

Severity: Medium

ID: 328841

File Name: al2_ALAS-2026-3798.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 7/21/2026

Updated: 7/21/2026

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: 3.5

Percentile: 52.03

CVSS v2

Risk Factor: Medium

Base Score: 6.2

Temporal Score: 4.6

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

CVSS Score Source: CVE-2026-11850

CVSS v3

Risk Factor: Medium

Base Score: 5

Temporal Score: 4.4

Vector: CVSS:3.0/AV:N/AC:H/PR:H/UI:N/S:U/C:L/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:krb5-debuginfo, p-cpe:/a:amazon:linux:krb5-devel, p-cpe:/a:amazon:linux:krb5-libs, p-cpe:/a:amazon:linux:krb5-pkinit, p-cpe:/a:amazon:linux:krb5-server-ldap, p-cpe:/a:amazon:linux:krb5-server, p-cpe:/a:amazon:linux:krb5-workstation, p-cpe:/a:amazon:linux:libkadm5

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

Exploit Ease: No known exploits are available

Patch Publication Date: 7/20/2026

Vulnerability Publication Date: 6/11/2026

Reference Information

CVE: CVE-2026-11850

Detections

Analytics