Bug 2479762 (CVE-2026-4408)

Summary:	CVE-2026-4408 samba: Remote Code Execution in SAMR
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	rhel-process-autobot, security-response-team, villapla, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in Samba. A remote attacker can exploit a misconfiguration in Samba file servers and classic domain controllers that use the "check password script" feature. If this script is configured with the %u substitution character, the client-controlled username is passed without proper escaping of shell meta-characters. This vulnerability allows an attacker to achieve remote command execution on the affected system. This issue primarily affects non-standard configurations where the "check password script" is used with %u and the samba-dcerpcd service is started as a system service.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2497358
Bug Blocks:
Deadline:	2026-05-26

Description OSIDB Bzimport 2026-05-19 09:27:20 UTC

Samba file servers and classic (non-AD) domain controllers offer the
SamValidatePasswordChange and SamValidatePasswordReset RPC services on the
SAMR DCE/RPC service when running over NCACN_IP_TCP. Both services pass a
username and password to the "check password script" that can be configured
in smb.conf.

If the "check password script" is configured with the %u
substitution character, the client-controlled username is passed to
the "check password script" without escaping shell meta-characters,
leading to a remote command execution vulnerability.

This is a non-standard configuration in several ways:

It affects Samba file servers and classic (non-AD) domain controllers
that have the "check password script" configured with the %u
substitution character. Active Directory Domain Controllers are not
affected, they do not expand the username via the %u substitution
character.

The problem is much less dangerous if %u has single quotes directly
around it, e.g. '%u', but it's still possible to inject
command line options.

Standard Samba file servers and classic domain controllers are also
only affected if the samba-dcerpcd service is started as a system
service, which can only happen if "rpc start on demand helpers" is set
to the non-default setting "no". In the default configuration for
DCE/RPC, smbd starts the samba-dcerpcd in a way that makes the
vulnerable code inaccessible.

Comment 2 errata-xmlrpc 2026-06-03 02:49:55 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:22644 https://access.redhat.com/errata/RHSA-2026:22644

Comment 3 errata-xmlrpc 2026-06-03 20:58:05 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10

Via RHSA-2026:22963 https://access.redhat.com/errata/RHSA-2026:22963

Comment 4 errata-xmlrpc 2026-06-10 11:14:54 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9

Via RHSA-2026:25049 https://access.redhat.com/errata/RHSA-2026:25049

Comment 5 errata-xmlrpc 2026-06-15 14:11:18 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.6 Extended Update Support

Via RHSA-2026:25979 https://access.redhat.com/errata/RHSA-2026:25979

Comment 6 errata-xmlrpc 2026-06-23 00:41:43 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On

Via RHSA-2026:28058 https://access.redhat.com/errata/RHSA-2026:28058

Comment 7 errata-xmlrpc 2026-06-23 00:54:17 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support
  Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On

Via RHSA-2026:28057 https://access.redhat.com/errata/RHSA-2026:28057

Comment 8 errata-xmlrpc 2026-06-23 00:54:29 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions
  Red Hat Enterprise Linux 8.8 Telecommunications Update Service

Via RHSA-2026:28056 https://access.redhat.com/errata/RHSA-2026:28056

Comment 9 errata-xmlrpc 2026-06-23 00:54:39 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 10.0 Extended Update Support

Via RHSA-2026:28055 https://access.redhat.com/errata/RHSA-2026:28055

Comment 10 errata-xmlrpc 2026-06-23 00:57:56 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions

Via RHSA-2026:28054 https://access.redhat.com/errata/RHSA-2026:28054

Comment 11 errata-xmlrpc 2026-06-23 00:58:14 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions

Via RHSA-2026:28053 https://access.redhat.com/errata/RHSA-2026:28053

Comment 12 errata-xmlrpc 2026-06-23 06:28:42 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7 Extended Lifecycle Support

Via RHSA-2026:28132 https://access.redhat.com/errata/RHSA-2026:28132

Comment 13 errata-xmlrpc 2026-06-30 11:06:33 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.21

Via RHSA-2026:29833 https://access.redhat.com/errata/RHSA-2026:29833

Comment 14 errata-xmlrpc 2026-06-30 13:45:25 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.20

Via RHSA-2026:29799 https://access.redhat.com/errata/RHSA-2026:29799

Comment 15 errata-xmlrpc 2026-07-02 18:30:09 UTC

This issue has been addressed in the following products:

  Red Hat OpenShift Container Platform 4.19

Via RHSA-2026:29863 https://access.redhat.com/errata/RHSA-2026:29863