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

> Remote attackers can execute arbitrary commands on Samba servers if the check password script uses unescaped user input.

- **Severity:** Critical 9.0 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 28 May 2026
- **Updated:** 8 Oct 2026
- **Also known as:** ALPINE-CVE-2026-4408, AZL-88883, CLSA-2026-1781175722, CLSA-2026-1781181291, CLSA-2026-1781186905, CLSA-2026-1781258405, CLSA-2026-1781343925, CLSA-2026-1781620050, CLSA-2026-1781627407, CLSA-2026-1782204526, CLSA-2026-1782977299, CLSA-2026-1782977935, CLSA-2026-1782988187, CLSA-2026-1782990961, DEBIAN-CVE-2026-4408, ECHO-e406-9590-08f0, GHSA-jg8v-92xc-cx65, UBUNTU-CVE-2026-4408

## What is CVE-2026-4408?

CVE-2026-4408 is a critical command injection vulnerability in Redhat Enterprise Linux, published on 28 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2026-4408?

It affects 3 products.


Products: Redhat Enterprise Linux, Redhat Openshift Container Platform, Samba Samba.

## How do I fix CVE-2026-4408?

Apply the vendor's patch.

## Is CVE-2026-4408 being exploited?

There is no known exploitation of CVE-2026-4408 in the wild and no public exploit code.

Public exploit code:

- proof-of-concept scripts for 2 unauthenticated RCEs in Samba (CVE-2026-4408 & CVE-2026-4480) and local privilege escalation in TelnetD (CVE-2026-28372) (github_poc): https://github.com/SafeBreach-Labs/ForgottenButNotGone

## Other vulnerabilities in Redhat Enterprise Linux

- [CVE-2018-14667](https://insights.sbomify.com/CVE-2018-14667/): Red Hat JBoss RichFaces Framework Expression Language Injection (critical 9.8, exploited in the wild)
- [CVE-2021-20325](https://insights.sbomify.com/CVE-2021-20325/): Missing fixes for CVE-2021-40438 and CVE-2021-26691 in the versions of httpd, as shipped in Red Hat Enterprise Linux 8.5.0, causes a securit (critical 9.8)
- [CVE-2018-25011](https://insights.sbomify.com/CVE-2018-25011/): Memory corruption in libwebp (critical 9.8)
- [CVE-2018-25014](https://insights.sbomify.com/CVE-2018-25014/): Other in libwebp (critical 9.8)
- [CVE-2014-3585](https://insights.sbomify.com/CVE-2014-3585/): Supply chain in redhat-upgrade-tool (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4408 and fix it if it is affected.

What it is: CVE-2026-4408 is a critical command injection vulnerability in Redhat Enterprise Linux, published on 28 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-4408 in the wild and no public exploit code.

Affected product: Redhat Enterprise Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-4408/ (Markdown: https://insights.sbomify.com/CVE-2026-4408/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4408
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4408
- OSV: https://osv.dev/vulnerability/CVE-2026-4408

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4408/
Summaries are generated and may contain mistakes; the official description above is the record.