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CVE-2026-4408

Samba command injection

9.0 CRITICALEPSS 1.75%
  1. Published28 May 2026

Description

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityHigh
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected products

Redhat Openshift Container Platform4.0
Samba≥ 4.1.0 < 4.21.0
Redhat Enterprise Linux6.0 · 7.0 · 9.0

Remediation

Fixed in
Samba≥ 4.21.0

References

and 15 more references

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Frequently asked

Is CVE-2026-4408 being actively exploited?

CVE-2026-4408 is not in the CISA KEV catalog. Its EPSS exploit probability is 1.75%.

How severe is CVE-2026-4408?

CVE-2026-4408 has a CVSS 3.1 base score of 9.0, rated critical. EPSS estimates a 1.75% probability of exploitation.

Which products are affected by CVE-2026-4408?

Affected products include Redhat Openshift Container Platform, Samba, Redhat Enterprise Linux.

How do I fix CVE-2026-4408?

Upgrade affected software to a fixed version, for example Samba 4.21.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-4408 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.