RCE in Samba
CVE-2026-4408
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.
Vulnerability class: Command Injection (OS Command Injection)
EPSS: 0.025 (83.6th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 9.0 (Critical). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H.
Affected products
- Samba
- Red Hat Enterprise Linux 10 — versions 0:4.23.5-109.el10_2
- Red Hat Enterprise Linux 10.0 Extended Update Support — versions 0:4.21.3-114.el10_0.1
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 7 Extended Lifecycle Support — versions 0:4.10.16-26.el7_9.1
- Red Hat Enterprise Linux 8 — versions 0:4.19.4-16.el8_10
- Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support — versions 0:4.13.3-12.el8_4.1
- Red Hat Enterprise Linux 8.4 Extended Update Support Long-life Add-on — versions 0:4.13.3-12.el8_4.1
- Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support — versions 0:4.15.5-16.el8_6.1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- secalert@redhat.com (x_refsource_REDHAT, Third Party Advisory, vdb-entry)
- secalert@redhat.com (x_refsource_REDHAT, issue-tracking, Third Party Advisory, Issue Tracking)
- secalert@redhat.com (Issue Tracking, Vendor Advisory)
- secalert@redhat.com (x_refsource_REDHAT, vendor-advisory, Issue Tracking)
- secalert@redhat.com (x_refsource_REDHAT, vendor-advisory, Issue Tracking)
- secalert@redhat.com (x_refsource_REDHAT, vendor-advisory)
- secalert@redhat.com (x_refsource_REDHAT, vendor-advisory)
- secalert@redhat.com (x_refsource_REDHAT, vendor-advisory)
- secalert@redhat.com (x_refsource_REDHAT, vendor-advisory)
- secalert@redhat.com (x_refsource_REDHAT, vendor-advisory)
Frequently asked questions
- What is CVE-2026-4408?
- CVE-2026-4408 is a critical-severity vulnerability in Samba, classified under OS Command Injection. CVSS score: 9.0/10. Published 2026-05-28.
- How severe is CVE-2026-4408?
- Critical severity. CVSS v3 base score is 9.0 out of 10.
- Is CVE-2026-4408 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.