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Nginx ControllerWeb server / proxy · F5

CVE-2020-27730

CRITICAL · 9.8 CVSS v3.1 Published 2020-12-11
Fix available
A fix is available. Upgrade to 3.10.0 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges 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 versions 3.0.0-3.9.0, 2.0.0-2.9.0, and 1.0.1, the NGINX Controller Agent does not use absolute paths when calling system utilities.

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

The NGINX Controller Agent (versions 1.0.1 and 2.0.0-3.9.0) does not use absolute paths when calling system utilities, allowing an attacker with control over the PATH environment variable or the ability to place malicious executables in searched directories to achieve arbitrary command execution. This path injection vulnerability enables privilege escalation to root-level access due to the agent's elevated privileges.

MitigationReplace all relative system utility invocations with absolute paths and explicitly set the PATH environment variable to trusted directories only, ensuring no user-controlled directories are included.

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
Nginx ControllerWeb server / proxy
Affected:>= 2.0.0, <= 2.9.0>= 3.0.0, < 3.10.0= 1.0.1
Cloud BackupApplication
Affected:all versions

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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/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. Identify if NGINX Controller Agent is installed
    Check for running nginx-controller-agent processes or look for agent-related packages/services on the system
    Affected if The NGINX Controller Agent process or installation is found on the system
  2. Determine the installed version
    Use the system's package manager or check the agent's version flag (such as nginx-controller-agent --version or similar) to identify the exact version number
    Affected if The version falls within 1.0.1, or >= 2.0.0 and <= 2.9.0, or >= 3.0.0 and < 3.10.0
  3. Inspect the agent process environment
    Retrieve the environment variables of the running NGINX Controller Agent process, specifically examining the PATH variable
    Affected if The PATH environment variable for the agent process includes user-writable directories or directories outside of trusted system paths (such as /usr/bin, /bin, /usr/sbin, /sbin)
  4. Check for relative path usage in agent scripts or configurations
    Review any scripts, configuration files, or execution logs from the NGINX Controller Agent for system utility calls that do not use absolute paths (e.g., 'curl' instead of '/usr/bin/curl')
    Affected if The agent invokes system utilities using relative command names without absolute paths

The system is affected if the NGINX Controller Agent version is 1.0.1 or falls within 2.0.0-2.9.0 or 3.0.0-3.10.0 and the agent's process environment or execution patterns show use of relative paths for system utilities with a potentially controllable PATH.

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 3.10.0 or later
Fixed in 3.10.0
Interim mitigation

Replace all relative system utility invocations with absolute paths and explicitly set the PATH environment variable to trusted directories only, ensuring no user-controlled directories are included.

Recommended fix Moderate confidence

NGINX Controller 3.10.0 or later (latest stable 3.x release recommended)

  1. 1. Identify the current installed version of NGINX Controller using the controller CLI or web interface
  2. 2. For NGINX Controller: Upgrade to version 3.10.0 or later to receive the fix for the path traversal vulnerability
  3. 3. For Cloud Backup: Contact F5 Networks support for available patches or mitigations, as all versions are affected
  4. 4. After upgrade, verify that system utility calls use absolute paths by reviewing system configurations
  5. 5. Test the upgraded system to ensure normal operation
Caveat Review F5 release notes for 3.10.0 for any breaking changes or migration considerations before upgrading

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

Fix this in Nginx Controller Scoped from the published advisory
  • Consultation8.0 h
  • Implementation24.0 h
  • Testing12.0 h
  • Review / QA8.0 h
52.0 hours of engineering $9,160
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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-2020-27730 in production — separate from our analysis above.

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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