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CVE-2026-4408

CRITICALCVSS 9.8/10EPSS 2.50%

Last modified

CVE-2026-4408 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. EPSS estimates a 2.50% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability
2.50%

82.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
RedhatOpenshift Container Platform4.0
SambaSamba>= 4.1.0, < 4.21.0
RedhatEnterprise Linux6.0
RedhatEnterprise Linux7.0
RedhatEnterprise Linux9.0

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is 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.
How severe is CVE-2026-4408?
CVE-2026-4408 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 2.50% probability of exploitation in the next 30 days.
How do I fix CVE-2026-4408?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST