# CVE-2026-4408: Samba: remote code execution in samr

Status: published. Published: 2026-05-28. Updated: 2026-11-03.

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.

## Remediation

- workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. (source: CNA: redhat)
- fix: RHSA-2026:28132: Red Hat Enterprise Linux Server (v. 7 ELS), Red Hat Enterprise Linux Server Optional (v. 7 ELS), Red Hat Enterprise Linux Server ResilientStorage (v. 7 ELS)

RHSA-2026:59831: Red Hat OpenShift Container Platform 4.12

RHSA-2026:65839: Red Hat OpenShift Container Platform 4.13

RHSA-2026:56786: Red Hat OpenShift Container Platform 4.14

RHSA-2026:56911: Red Hat OpenShift Container Platform 4.15

RHSA-2026:56853: Red Hat OpenShift Container Platform 4.16

RHSA-2026:60019: Red Hat OpenShift Container Platform 4.17

RHSA-2026:57483: Red Hat OpenShift Container Platform 4.18

RHSA-2026:29863: Red Hat OpenShift Container Platform 4.19

RHSA-2026:29799: Red Hat OpenShift Container Platform 4.20

RHSA-2026:29833: Red Hat OpenShift Container Platform 4.21

RHSA-2026:28055: Red Hat Enterprise Linux AppStream EUS (v. 10.0), Red Hat Enterprise Linux BaseOS EUS (v. 10.0), Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0)

RHSA-2026:22963: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)

RHSA-2026:22644: Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux BaseOS (v. 8), Red Hat Enterprise Linux CRB (v. 8)

RHSA-2026:28057: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6), Red Hat Enterprise Linux BaseOS AUS (v.8.6), Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6)

RHSA-2026:28056: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8), Red Hat Enterprise Linux BaseOS E4S (v.8.8), Red Hat Enterprise Linux BaseOS TUS (v.8.8)

RHSA-2026:28054: Red Hat Enterprise Linux AppStream E4S (v.9.2), Red Hat Enterprise Linux BaseOS E4S (v.9.2), Red Hat Enterprise Linux Resilient Storage E4S (v.9.2)

RHSA-2026:28053: Red Hat Enterprise Linux AppStream E4S (v.9.4), Red Hat Enterprise Linux BaseOS E4S (v.9.4), Red Hat Enterprise Linux Resilient Storage E4S (v.9.4)

RHSA-2026:25979: Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux AppStream EUS (v.9.6), Red Hat Enterprise Linux BaseOS EUS (v.9.6), Red Hat Enterprise Linux Resilient Storage EUS (v.9.6)

RHSA-2026:25049: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9), Red Hat Enterprise Linux Resilient Storage (v. 9)

RHSA-2026:28058: Red Hat Enterprise Linux BaseOS AUS (v.8.4), Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) (source: ADP: redhat-SADP)
- workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. (source: ADP: redhat-SADP)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (samba): ≥ 0:4.23.5-109.el10_2; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10.0 Extended Update Support (samba): ≥ 0:4.21.3-114.el10_0.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 Extended Lifecycle Support (samba): ≥ 0:4.10.16-26.el7_9.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (samba): ≥ 0:4.19.4-16.el8_10; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support (samba): ≥ 0:4.13.3-12.el8_4.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On (samba): ≥ 0:4.13.3-12.el8_4.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support (samba): ≥ 0:4.15.5-16.el8_6.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On (samba): ≥ 0:4.15.5-16.el8_6.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.8 Telecommunications Update Service (samba): ≥ 0:4.17.5-7.el8_8.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions (samba): ≥ 0:4.17.5-7.el8_8.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (samba): ≥ 0:4.23.5-10.el9_8; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions (samba): ≥ 0:4.17.5-105.el9_2.5; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions (samba): ≥ 0:4.19.4-105.el9_4.4; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9.6 Extended Update Support (samba): ≥ 0:4.21.3-14.el9_6.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.12 (openshift/ose-rhel-coreos-8): ≥ 412.86.202608241157-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.13 (openshift/ose-rhel-coreos-9): ≥ 413.92.202609080414-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.14 (openshift/ose-rhel-coreos-9): ≥ 414.92.202608172040-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.15 (openshift/ose-rhel-coreos-9): ≥ 415.92.202608180329-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.16 (openshift/ose-rhel-coreos-9): ≥ 416.94.202608150307-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.17 (openshift/ose-rhel-coreos-9): ≥ 417.94.202608250221-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.18 (openshift/ose-rhel-coreos-9): ≥ 418.94.202608142238-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.19 (openshift/ose-rhel-coreos-9): ≥ 4.19.9.6.202606241344-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.20 (openshift/ose-rhel-coreos-9): ≥ 4.20.9.6.202606241928-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4.21 (openshift/ose-rhel-coreos-9): ≥ 4.21.9.6.202606241859-0; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (samba): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (samba4): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 10 (samba): ≥ 0:4.23.5-109.el10_2; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 10.0 Extended Update Support (samba): ≥ 0:4.21.3-114.el10_0.1; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 7 Extended Lifecycle Support (samba): ≥ 0:4.10.16-26.el7_9.1; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 8 (samba): ≥ 0:4.19.4-16.el8_10; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support (samba): ≥ 0:4.13.3-12.el8_4.1; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On (samba): ≥ 0:4.13.3-12.el8_4.1; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support (samba): ≥ 0:4.15.5-16.el8_6.1; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On (samba): ≥ 0:4.15.5-16.el8_6.1; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 8.8 Telecommunications Update Service (samba): ≥ 0:4.17.5-7.el8_8.1; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions (samba): ≥ 0:4.17.5-7.el8_8.1; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 9 (samba): ≥ 0:4.23.5-10.el9_8; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions (samba): ≥ 0:4.17.5-105.el9_2.5; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions (samba): ≥ 0:4.19.4-105.el9_4.4; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 9.6 Extended Update Support (samba): ≥ 0:4.21.3-14.el9_6.1; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.12 (rhcos): ≥ 412.86.202608241157-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.13 (rhcos): ≥ 413.92.202609080414-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.14 (rhcos): ≥ 414.92.202608172040-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.15 (rhcos): ≥ 415.92.202608180329-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.16 (rhcos): ≥ 416.94.202608150307-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.17 (rhcos): ≥ 417.94.202608250221-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.18 (rhcos): ≥ 418.94.202608142238-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.19 (rhcos): ≥ 4.19.9.6.202606241344-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.20 (rhcos): ≥ 4.20.9.6.202606241928-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4.21 (rhcos): ≥ 4.21.9.6.202606241859-0; < * (unaffected, rpm). Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 6 (samba): Version range not reported. Source: ADP: redhat-SADP
- Red Hat / Red Hat Enterprise Linux 6 (samba4): Version range not reported. Source: ADP: redhat-SADP
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-8): Version range not reported. Source: ADP: redhat-SADP

## Severity and prioritization

- CVSS 3.1: 9 (critical); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H; source: CNA: redhat

- CVSS 3.1: 9 (critical); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H; source: ADP: redhat-SADP

- CISA KEV: No listing in collected sources

- EPSS: 2.50% as of 2026-11-03; percentile 84.72%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-78

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/errata/RHSA-2026:22644 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:22963 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:25049 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:25979 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28053 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28054 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28055 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28056 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28057 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28058 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28132 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:29799 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:29833 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:29863 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:56786 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:56853 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:56911 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:57483 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:59831 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:60019 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:65839 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-4408 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2479762 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://bugzilla.samba.org/show_bug.cgi?id=16034 (CNA: redhat)

- https://access.redhat.com/security/cve/CVE-2026-4408 (ADP: redhat-SADP; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2479762 (ADP: redhat-SADP; issue-tracking, x_refsource_REDHAT)

- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-4408.json (ADP: redhat-SADP; x_sadp-csaf-vex)

- https://access.redhat.com/errata/RHSA-2026:28132 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:59831 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:65839 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:56786 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:56911 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:56853 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:60019 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:57483 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:29863 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:29799 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:29833 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28055 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:22963 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:22644 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28057 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28056 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28054 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28053 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:25979 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:25049 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:28058 (ADP: redhat-SADP; vendor-advisory, x_refsource_REDHAT)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-4408; retrieved 2026-11-03; source updated 2026-11-03

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-4408; retrieved 2026-11-03; source updated Not reported

Revision: 2a16a9850e879d6b5fb1838a7a343d763b8b032f53e4258b6d583017042a148d

Canonical: https://y2.dev/cve/CVE-2026-4408

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