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SystemdApplication · Systemd Project

CVE-2026-40226

MEDIUM · 6.4 CVSS v3.1 Published 2026-04-10
Fix available
A fix is available. Upgrade to 257.12 / 258.6 or later.
See remediation →
66/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In nspawn in systemd 233 through 259 before 260, an escape-to-host action can occur via a crafted optional config file.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A container escape vulnerability exists in systemd-nspawn (versions 233-259) where a specially crafted optional configuration file can allow an attacker to break out of the containerized environment and execute actions on the host system. This bypasses the isolation boundary between the container and host.

MitigationUpgrade systemd to version 260 or later. For systems that cannot upgrade immediately, avoid using untrusted container configuration files and ensure container images are from verified sources.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
SystemdApplication
Affected:>= 233, < 257.12>= 258, < 258.6>= 259, < 259.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
High
Privileges
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify systemd-nspawn is installed
    Run 'which systemd-nspawn' or check if the binary exists at /usr/bin/systemd-nspawn
    Affected if systemd-nspawn binary exists on the system
  2. Determine installed systemd version
    Run 'systemd --version' and examine the version number in the output
    Affected if version is 233 through 257.11, or 258.0 through 258.5, or 259.0 through 259.3
  3. Locate container configuration files
    Check common locations for systemd-nspawn config such as /etc/nspawn/, ~/.config/systemd/nspawn/, or directories containing .nspawn files
    Affected if any .nspawn or nspawn.conf configuration files are present in these directories
  4. Inspect configuration file contents
    Examine any found configuration files for suspicious or unusual settings, particularly those that may reference host resources or bind mounts
    Affected if configuration files contain bind mount directives or settings that could allow host access

The system is affected if systemd-nspawn is present AND the installed systemd version falls within 233-257.11, 258-258.5, or 259-259.3 AND untrusted or attacker-controlled configuration files could be loaded by nspawn.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 257.12 / 258.6 / 259.4 or later
Fixed in 257.12258.6259.4
Interim mitigation

Upgrade systemd to version 260 or later. For systems that cannot upgrade immediately, avoid using untrusted container configuration files and ensure container images are from verified sources.

Recommended fix High confidence

Upgrade to systemd 260 or later (the version that contains the fix for this nspawn escape-to-host vulnerability)

  1. Identify your current systemd version using: systemd --version
  2. If running systemd >= 233 and < 257.12: upgrade to at least 257.12, or preferably to version 260 or later
  3. If running systemd >= 258 and < 258.6: upgrade to at least 258.6, or preferably to version 260 or later
  4. If running systemd >= 259 and < 259.4: upgrade to at least 259.4, or preferably to version 260 or later
  5. Verify the upgrade was successful by running: systemd --version
  6. If using systemd-nspawn containers, ensure any custom optional configuration files are reviewed for unexpected content
Caveat Major version upgrades of systemd may include changes to unit file syntax, behavior, or deprecated features; review release notes before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Systemd Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-40226 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data