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F5os AOperating system · F5

CVE-2025-36546

HIGH · 8.1 CVSS v3.1 Published 2025-05-07
Fix available
A fix is available. Upgrade to 1.5.3 or later.
See remediation →
90/100
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
On an F5OS system, if the root user had previously configured the system to allow login via SSH key-based authentication, and then enabled Appliance Mode; access via SSH key-based authentication is still allowed. For an attacker to exploit this vulnerability they must obtain the root user's SSH private key.   Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

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 · high confidence

On F5OS systems, enabling Appliance Mode fails to properly disable SSH key-based authentication for the root user, creating a security bypass where root can still authenticate via SSH keys even when Appliance Mode should restrict such access. An attacker who obtains the root user's SSH private key can exploit this to gain root access to the system.

MitigationBefore enabling Appliance Mode, explicitly disable SSH key-based authentication for the root user, or rotate/secure the root SSH private keys if Appliance Mode must be used.

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
F5os AOperating system
Affected:>= 1.5.1, < 1.5.3
F5os COperating system
Affected:>= 1.6.0, <= 1.6.2

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/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 F5OS platform and version
    Run 'tmsh show sys version' or check the system dashboard to determine if the platform is F5os A or F5os C and note the exact installed version
    Affected if The installed version is F5os A >= 1.5.1 and < 1.5.3, or F5os C >= 1.6.0 and <= 1.6.2
  2. Verify if Appliance Mode is enabled
    Check the Appliance Mode status in the F5OS administrative interface or via 'tmsh show sys appliance' command
    Affected if Appliance Mode is currently enabled on the system
  3. Examine root user SSH key-based authentication configuration
    Review the SSH daemon configuration (typically /etc/ssh/sshd_config) for the root user and check whether PubkeyAuthentication or AuthorizedKeysFile directives permit key-based login
    Affected if SSH key-based authentication is permitted for root while Appliance Mode is enabled
  4. Check for existing root SSH authorized keys
    Inspect the root user's authorized_keys file (commonly /root/.ssh/authorized_keys or as configured in sshd_config) and list any present SSH public keys
    Affected if Any SSH authorized keys exist for the root user while running the affected version with Appliance Mode enabled

A system is affected if it runs a vulnerable F5OS version (A: 1.5.1 to <1.5.3, C: 1.6.0 to 1.6.2), has Appliance Mode enabled, and still permits root SSH key-based authentication despite the mode being intended to restrict such access.

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 1.5.3 or later
Fixed in 1.5.3
Interim mitigation

Before enabling Appliance Mode, explicitly disable SSH key-based authentication for the root user, or rotate/secure the root SSH private keys if Appliance Mode must be used.

Recommended fix High confidence

F5os A: 1.5.3 or later; F5os C: version beyond 1.6.2 (e.g., 1.6.3 or later)

  1. 1. Identify the current F5OS version by running: tmsh show sys version
  2. 2. For F5os A: If version is >= 1.5.1 and < 1.5.3, plan upgrade to 1.5.3 or later
  3. 3. For F5os C: If version is >= 1.6.0 and <= 1.6.2, plan upgrade to a version beyond 1.6.2 (such as 1.6.3)
  4. 4. Before upgrading, review the F5OS upgrade guide at my.f5.com for your specific platform
  5. 5. Perform the upgrade following F5 best practices: backup configuration, verify upgrade package integrity, schedule maintenance window
  6. 6. After upgrade, verify Appliance Mode is properly enforcing security (SSH key-based auth should be disabled for root in Appliance Mode)
  7. 7. Confirm the fix by checking that root login via SSH keys is no longer possible when Appliance Mode is enabled

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

Fix this in F5os A Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA2.0 h
10.0 hours of engineering $1,770
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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-2025-36546 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