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CVE Record

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.

CriticalCVSS 9Not KEV-listedUpdated
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Glexia's TakeAutomated analysiscritical

Security readout for executives and security teams

Plain-English summary

CVE-2026-4408 is a critical Samba remote code execution issue, but exposure depends on a specific non-standard configuration. Systems are at risk when Samba uses the check password script feature with %u, allowing a client-controlled username to reach a shell without proper escaping.

Executive priority

Treat this as urgent for environments running Samba in identity or file-sharing roles, especially domain controllers. The practical priority is configuration-driven: quickly identify whether the risky feature is enabled, then apply vendor guidance and updates to confirmed exposures.

Technical view

The flaw is CWE-78 command injection in Samba samr handling. A remote unauthenticated attacker may trigger command execution where check password script includes %u and samba-dcerpcd runs as a system service. CVSS is 9.0 with high confidentiality, integrity, and availability impact.

Likely exposure

Most likely exposed assets are Samba file servers or classic domain controllers on listed Red Hat platforms using check password script with %u. The bundle lists affected RHEL 7 ELS, 8, 9, 10 variants and OpenShift Container Platform 4.19 to 4.21 rhcos.

Exploitation context

The source bundle marks KEV as false and provides no evidence of active exploitation. Exploitation is network-reachable and unauthenticated in the CVSS vector, but attack complexity is high because the vulnerable configuration is specific and non-default.

Researcher notes

Evidence supports a configuration-dependent RCE, not broad exploitation of all Samba installations. Avoid assuming exposure from package presence alone. Validate the %u substitution path, service context, and affected Red Hat product stream before assigning incident-level urgency.

Mitigation direction

  • Review Red Hat and Samba advisories for supported updates or configuration guidance.
  • Remove %u from check password script usage unless vendor guidance explicitly permits it.
  • Disable unused check password script configurations on Samba servers.
  • Prioritize updates for internet-facing or domain-controller Samba systems.
  • Restrict network access to Samba services where business requirements allow.

Validation and detection

  • Inventory Samba servers and classic domain controllers across listed Red Hat platforms.
  • Check smb.conf for check password script entries using %u.
  • Confirm whether samba-dcerpcd runs as a system service on candidate hosts.
  • Map installed samba or rhcos versions to referenced Red Hat advisories.
  • Review authentication-related logs for suspicious username-driven failures or script errors.
Prepared
Confidence
high
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-78: Command execution behavior lookup

Command injection weaknesses can lead defenders to review execution techniques and command interpreter telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
description · low confidence lookup

Credential and access behavior lookup

The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

Open ATT&CK lookup
description · low confidence lookup

Container behavior lookup

The affected technology mentions containers, so container-specific ATT&CK technique review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2026-4408 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
Critical
CVSS
9 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
7Timeline events
2ADP providers
19Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: total

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
9CVSS 3.1CriticalCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H2.26redhat
9CVSS 3.1CriticalCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H2.26redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

9Critical
CVSS 3.1 vector shape for CVE-2026-4408Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Reported to Red Hat.

  3. Source timelineredhat

    Reported to Red Hat.

  4. ADP timelineredhat-SADP

    Made public.

  5. Source timelineredhat

    Made public.

  6. CVE publishedCVE Program

    The CVE record was published.

  7. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPsamba: Remote Code Execution in SAMR
other:Red Hat severity ratingcvssV3_1
  • 2026-05-19T09:24:56.961Z: Reported to Red Hat.
  • 2026-05-26T00:00:00.000Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Red HatRed Hat Enterprise Linux 10samba, 0:4.23.5-109.el10_2affected
Red HatRed Hat Enterprise Linux 10.0 Extended Update Supportsamba, 0:4.21.3-114.el10_0.1affected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Supportsamba, 0:4.10.16-26.el7_9.1affected
Red HatRed Hat Enterprise Linux 7 Extended Lifecycle Supportsamba, 0:4.10.16-26.el7_9.1affected
Red HatRed Hat Enterprise Linux 8samba, 0:4.19.4-16.el8_10affected
Red HatRed Hat Enterprise Linux 8samba, 0:4.19.4-16.el8_10affected
Red HatRed Hat Enterprise Linux 8.4 Advanced Mission Critical Update Supportsamba, 0:4.13.3-12.el8_4.1affected
Red HatRed Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-Onsamba, 0:4.13.3-12.el8_4.1affected
Red HatRed Hat Enterprise Linux 8.6 Advanced Mission Critical Update Supportsamba, 0:4.15.5-16.el8_6.1affected
Red HatRed Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-Onsamba, 0:4.15.5-16.el8_6.1affected
Red HatRed Hat Enterprise Linux 8.8 Telecommunications Update Servicesamba, 0:4.17.5-7.el8_8.1affected
Red HatRed Hat Enterprise Linux 8.8 Update Services for SAP Solutionssamba, 0:4.17.5-7.el8_8.1affected
Red HatRed Hat Enterprise Linux 9samba, 0:4.23.5-10.el9_8affected
Red HatRed Hat Enterprise Linux 9samba, 0:4.23.5-10.el9_8affected
Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutionssamba, 0:4.17.5-105.el9_2.5affected
Red HatRed Hat Enterprise Linux 9.4 Update Services for SAP Solutionssamba, 0:4.19.4-105.el9_4.4affected
Red HatRed Hat Enterprise Linux 9.6 Extended Update Supportsamba, 0:4.21.3-14.el9_6.1affected
Red HatRed Hat OpenShift Container Platform 4.19rhcos, 4.19.9.6.202606241344-0affected
Red HatRed Hat OpenShift Container Platform 4.20rhcos, 4.20.9.6.202606241928-0affected
Red HatRed Hat OpenShift Container Platform 4.21rhcos, 4.21.9.6.202606241859-0affected
Red HatRed Hat Enterprise Linux 6sambaunknown
Red HatRed Hat Enterprise Linux 6samba4unknown
Weakness

CWE details

CWE-78

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-78 · source CWE mapping

Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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