CVE-2026-4408 | 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.

Published: 2026-05-28 Last update: 2026-06-04 Assigner: [email protected] Source: [email protected]
NVD Status：Undergoing Analysis，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-4408 is rated Moderate Risk (57.3/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 0.39%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-4408

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-03 0.23% 0.39% +0.16%
2 2026-05-28 — 0.23% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-4408

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.0 3.1 CRITICAL
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.2 6.0 [email protected]

Weakness enumeration for CVE-2026-4408

GitHub Security Advisory for CVE-2026-4408

GHSA-jg8v-92xc-cx65 · Severity: critical — A flaw was found in Samba. A remote attacker can exploit a misconfiguration in Samba file servers...

OS Trackers for CVE-2026-4408

vendor priority summary link
debian not yet assigned CVE-2026-4408 not yet assigned priority: Debian including 1 source packages (samba), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1. https://security-tracker.debian.org/tracker/CVE-2026-4408
redhat high — https://access.redhat.com/security/cve/CVE-2026-4408
suse critical CVE-2026-4408 severity critical: SUSE including 172 source package names (ctdb-4.15.13+git.701.449cb7f5cd3-3.106.1, ctdb-4.15.13+git.780.d2f53cbcded-150300.3.103.1, …), 468 product×package rows across 29 product lines (SUSE Enterprise Storage 7.1, SUSE Linux Enterprise High Availability Extension 12 SP5, … (29 product lines)): Fixed 271, First Fixed 197. https://www.suse.com/security/cve/CVE-2026-4408/
ubuntu medium CVE-2026-4408 medium priority: Ubuntu including 1 source packages (samba), 9 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): released 5, needs-triage 4. https://ubuntu.com/security/CVE-2026-4408

Affected software / configurations for CVE-2026-4408

Vendor Product Version Raw CPE
No affected products in dataset.

References for CVE-2026-4408

cvelogic Threat Intelligence