--- id: CVE-2026-4408 title: A flaw was found in Samba summary: >- 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 characte… severity: critical cvss: 9 cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H' cwe: - CWE-78 vendor: redhat product: openshift_container_platform affected: - openshift_container_platform = 4.0 - 'samba >= 4.1.0, < 4.21.0' - enterprise_linux = 6.0 - enterprise_linux = 7.0 - enterprise_linux = 9.0 patched: - samba 4.21.0 published: '2026-05-28' updated: '2026-09-18' sourceUpdated: '2026-09-18T13:18:31.373' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-4408' references: - url: 'https://access.redhat.com/errata/RHSA-2026:22644' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:22963' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:25049' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:25979' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:28053' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:28054' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:28055' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:28056' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:28057' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:28058' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:28132' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:29799' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:29833' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:29863' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:56786' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:56853' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:56911' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:57483' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:59831' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:60019' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:65839' label: secalert@redhat.com - url: 'https://access.redhat.com/security/cve/CVE-2026-4408' label: secalert@redhat.com - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2479762' label: secalert@redhat.com - url: 'https://bugzilla.samba.org/show_bug.cgi?id=16034' label: secalert@redhat.com - url: 'https://access.redhat.com/errata/RHSA-2026:22644' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:22963' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:25049' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:25979' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:28053' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:28054' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:28055' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:28056' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:28057' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:28058' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:28132' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:29799' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:29833' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:29863' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:56786' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:56853' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:56911' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:57483' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:59831' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:60019' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/errata/RHSA-2026:65839' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://access.redhat.com/security/cve/CVE-2026-4408' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2479762' label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4408.json label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c - url: 'https://www.cve.org/CVERecord?id=CVE-2026-4408' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-4408' tags: - nvd - exploit-available - cve.org - csaf - vex - red-hat epss: 0.0175 epssPercentile: 0.76851 exploits: github: 1 githubRepos: - 'https://github.com/SafeBreach-Labs/ForgottenButNotGone' checkedAt: '2026-09-25T08:20:57.486Z' exploitAvailable: true ssvc: exploitation: none automatable: 'no' technicalImpact: total timestamp: '2026-05-29T03:55:49.995145Z' ingestedAt: '2026-07-01T09:50:45.867Z' --- ## Overview 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. ## Affected - `openshift_container_platform = 4.0` - `samba >= 4.1.0, < 4.21.0` - `enterprise_linux = 6.0` - `enterprise_linux = 7.0` - `enterprise_linux = 9.0` ## Remediation Upgrade past the affected range: - `samba 4.21.0` ## Vendor advisories - **RHSA-2026:28132** · Red Hat · fixed in: Red Hat Enterprise Linux Server (v. 7 ELS), Red Hat Enterprise Linux Server ResilientStorage (v. 7 ELS), Red Hat Enterprise Linux Server Optional (v. 7 ELS) · released 2026-06-23 · [advisory](https://access.redhat.com/errata/RHSA-2026:28132) - **RHSA-2026:59831** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.12 · released 2026-09-03 · [advisory](https://access.redhat.com/errata/RHSA-2026:59831) - **RHSA-2026:65839** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.13 · released 2026-09-17 · [advisory](https://access.redhat.com/errata/RHSA-2026:65839) - **RHSA-2026:56786** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.14 · released 2026-08-31 · [advisory](https://access.redhat.com/errata/RHSA-2026:56786) - **RHSA-2026:56911** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.15 · released 2026-08-31 · [advisory](https://access.redhat.com/errata/RHSA-2026:56911) - **RHSA-2026:56853** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.16 · released 2026-08-31 · [advisory](https://access.redhat.com/errata/RHSA-2026:56853) - **RHSA-2026:60019** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.17 · released 2026-09-03 · [advisory](https://access.redhat.com/errata/RHSA-2026:60019) - **RHSA-2026:57483** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.18 · released 2026-08-26 · [advisory](https://access.redhat.com/errata/RHSA-2026:57483) - **RHSA-2026:29863** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.19 · released 2026-07-02 · [advisory](https://access.redhat.com/errata/RHSA-2026:29863) - **RHSA-2026:29799** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.20 · released 2026-06-30 · [advisory](https://access.redhat.com/errata/RHSA-2026:29799) - **RHSA-2026:29833** · Red Hat · fixed in: Red Hat OpenShift Container Platform 4.21 · released 2026-06-30 · [advisory](https://access.redhat.com/errata/RHSA-2026:29833) - **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 6, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat OpenShift Container Platform 4 · updated 2026-09-17 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4408.json)