Samba Remote Cmd Exec via Unsanitized %u in check password script
CVE-2026-4408 Published on May 28, 2026

Samba: remote code execution in samr
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.

Vendor Advisory Vendor Advisory Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-4408 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to be critical as this vulnerability has a high impact to the confidentiality, integrity and availability of this component.

Attack Vector:
NETWORK
Attack Complexity:
HIGH
Privileges Required:
NONE
User Interaction:
NONE
Scope:
CHANGED
Confidentiality Impact:
HIGH
Integrity Impact:
HIGH
Availability Impact:
HIGH

Timeline

Reported to Red Hat.

Made public. 7 days later.

Weakness Type

What is a Shell injection Vulnerability?

The software constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component.

CVE-2026-4408 has been classified to as a Shell injection vulnerability or weakness.


Products Associated with CVE-2026-4408

You can be notified by email with stack.watch whenever vulnerabilities like CVE-2026-4408 are published in these products:

Canonical Ubuntu Linux
 
Red Hat Enterprise Linux (RHEL)
 
Red Hat Openshift
 

Affected Versions

Red Hat Enterprise Linux 10: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 8: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 9: Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 6: Red Hat Enterprise Linux 7: Red Hat OpenShift Container Platform 4:

Exploit Probability

EPSS
0.39%
Percentile
60.57%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.