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RHEL 8 : krb5 (RHSA-2026:16799)

medium Nessus Plugin ID 314391

Synopsis

The remote Red Hat host is missing one or more security updates for krb5.

Description

The remote Redhat Enterprise Linux 8 host has packages installed that are affected by multiple vulnerabilities as referenced in the RHSA-2026:16799 advisory.

 Kerberos is a network authentication system, which can improve the security of your network by eliminating the insecure practice of sending passwords over the network in unencrypted form. It allows clients and servers to authenticate to each other with the help of a trusted third party, the Kerberos key distribution center (KDC).

 Security Fix(es):

 * krb5: MIT Kerberos 5 (krb5): Denial of Service via integer underflow and out-of-bounds read (CVE-2026-40356)

 * krb5: MIT Kerberos 5: Denial of Service via NULL pointer dereference in NegoEx mechanism (CVE-2026-40355)

 For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Tenable has extracted the preceding description block directly from the Red Hat Enterprise Linux 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

Update the RHEL krb5 package based on the guidance in RHSA-2026:16799.

See Also

https://access.redhat.com/security/updates/classification/#important

https://bugzilla.redhat.com/show_bug.cgi?id=2463368

https://bugzilla.redhat.com/show_bug.cgi?id=2463370

http://www.nessus.org/u?6d16fb88

https://access.redhat.com/errata/RHSA-2026:16799

Plugin Details

Severity: Medium

ID: 314391

File Name: redhat-RHSA-2026-16799.nasl

Version: 1.1

Type: Local

Agent: unix

Published: 5/13/2026

Updated: 5/13/2026

Supported Sensors: Nessus Agent, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

Vendor

Vendor Severity: Important

CVSS v2

Risk Factor: Medium

Base Score: 5.4

Temporal Score: 4

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

CVSS Score Source: CVE-2026-40356

CVSS v3

Risk Factor: Medium

Base Score: 5.9

Temporal Score: 5.2

Vector: CVSS:3.0/AV:N/AC:H/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:redhat:enterprise_linux:8, p-cpe:/a:redhat:enterprise_linux:krb5-devel, p-cpe:/a:redhat:enterprise_linux:krb5-libs, p-cpe:/a:redhat:enterprise_linux:krb5-server, p-cpe:/a:redhat:enterprise_linux:krb5-workstation, p-cpe:/a:redhat:enterprise_linux:krb5-server-ldap, p-cpe:/a:redhat:enterprise_linux:krb5-pkinit, p-cpe:/a:redhat:enterprise_linux:libkadm5, p-cpe:/a:redhat:enterprise_linux:krb5, cpe:/o:redhat:rhel_eus:8.10

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

Exploit Ease: No known exploits are available

Patch Publication Date: 5/13/2026

Vulnerability Publication Date: 4/28/2026

Reference Information

CVE: CVE-2026-40355, CVE-2026-40356

CWE: 191, 476

RHSA: 2026:16799