Vulnerability in samba (DEBIAN-CVE-2026-4408)

Summary

Vulnerability in samba (DEBIAN-CVE-2026-4408). Successful exploitation can lead to full system takeover. Mitigation: upgrade to 2:4.17.12+dfsg-0+deb12u4 or later.

Original description

The description as published by the source.

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.

Source: OSV.dev (Open Source Vulnerabilities) OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as DEBIAN-CVE-2026-4408 has been found in samba.
Successful exploitation can lead to full system takeover.
What to do: upgrade samba to 2:4.17.12+dfsg-0+deb12u4 or later.
If unsure, ask your IT team or search "samba DEBIAN-CVE-2026-4408" on the vendor's site.

DEBIAN-CVE-2026-4408 (samba)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 2:4.17.12+dfsg-0+deb12u4 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in samba.

📍 Affected scope

Check the vendor advisory for the affected versions of samba.

🔥 Severity

Severity: ?. Successful exploitation can lead to full system takeover.

🔧 How to fix

Update to 2:4.17.12+dfsg-0+deb12u4.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'samba' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'samba' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で samba を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade samba to 2:4.17.12+dfsg-0+deb12u4
```
ステージング環境で 2:4.17.12+dfsg-0+deb12u4 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
3
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

Debian:11 samba

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Debian:12 samba

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2:4.17.12+dfsg-0+deb12u4"}]}]

Debian:13 samba

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2:4.22.8+dfsg-0+deb13u2"}]}]

Debian:14 samba

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2:4.24.3+dfsg-1"}]}]

References

advisory security-tracker.debian.org