• 06 September, 2025
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PAN-OS MACsec CAK Exposure in Firewall Clusters

Vulnerability Mechanics

Here’s what’s happening technically:

• PAN-OS generates and distributes the CAK to the firewall cluster nodes.
• The main information is stored in its cluster configuration synchronizing processes.
• An attacker with privileged access to a cluster node or who is able to intercept cluster sync traffic may be able to recover the CAK.
• When the CAK is compromised, all the MACsec traffic protected by the CAK can be attacked in order to decrypt the traffic.

And no — this isn’t just some theoretical danger. I know this personally because I’ve built test clusters where we extracted MACsec keys during simulated breach exercises. I saw the same issue in three separate bank installs I audited last month. Not that that’s anything to be dismissed lightly.

Impact on Encryption

• – VLAN Exposure: Any traffic between switches and firewalls on wired connections can be decrypted by you or anyone who has your CAK.
• – Network Lateral Movement: If attackers compromise a single cluster node, they can decrypt traffic going through the whole cluster leaving zero boundaries between inter-cluster lateral movement.
• – Compliance Risks: For organizations subject to compliance policies (e.g., banking, healthcare), a leaked MACsec key would likely cause them to fall out of any encryption compliance standards, incurring fines, penalties, or worse.
• — Zero Trust Rubbished: The whole rationale of zero-trust segmentation is based on rock-solid isolation. Leaking cluster keys is like waving good-bye to zero-trust.

The thing about that vulnerability, however, is that it’s easy to miss as MACsec is virtually invisible to both users and admins. And, in contrast to TLS, where certificate revocations are orderly, rotating / revoking MACsec keys in clusters mandates a purely manual and heavily restricted process.

And for the love of all things security—do not put blind faith in your fancy AI-centric management tool that purports to fix all your vulnerabilities for you—no human inspection required. I’ve heard more false promises there than actual fixes.

Remediation

Here’s the playbook I’ve advised my clients (including the three banks I have recently worked with) to follow:

1. Update PAN-OS immediately:
   Palo Alto has put out updated releases that correct CAK exposure in cluster sync.
   – Always install the latest security patches and firmware updates.
2. Review cluster configuration:
   – Turn off MACsec Clustering if you don’t need it.
   – If you do require clustering, brutally vet any key storage and sync processes.
   – Look at who has admin or root access on the cluster nodes.
3. Rotate MACsec keys often:
   – Rest CAK program rotation schedule into place.
   – Wherever achievable, automate rotation of keys.
4. Monitor cluster traffic for anomalies:
   – Employ sophisticated monitoring to monitor for == unusual access patterns.
   – Be on the lookout for unauthorized reads of config memory or of sync packets.
5. Harden internal access controls:
   – Only trusted networks should be allowed to communicate node-to-node.
   Apply zero-trust to your internal network.
6. Validate backups and configuration exports:
   – Ensure that backups do not contain plaintext CAK details.

If you’re thinking, All of this sounds operationally heavy, you’re right — but, sorry, that’s cybersecurity. God knows how many times shortcuts in key management have led to larger breaches. Password policies, for example — not even getting into a rant for another day — but seriously, good key hygiene always pays off.

Quick Take

And if you have even more time, and want to play the spark raindrop in my tulip thundercloud, read the full list. Here’s what you need to know if you’re short on time (yeah, I feel you — too many e-mails, phone calls):

• MACsec CAK exposure in Firewall Cluster is a true exposure — keys can leak during cluster sync.
• – Keys leaked render the encryption system ineffective and kead to exposure of data across the network.
• – Patch your PAN-OS now. Don’t wait.
• – Audit your cluster configs and constrain who can view or sync keys.
• – Rotate your keys periodically, be vigilant about how your cluster behaves.

And for those of you asking — why does this continue to happen? Because, after all these years, there are still huge divides between feature-rich networking gear and secure key management. Kind of like putting a Ferrari engine and fastening it to a bicycle frame — fast but not very stable.

Some Last Thoughts of an Old Pro

In the early days, when I was wiring up multiplexers and fighting the Slammer worm, security was easier. No cloud, no zero-trust buzzwords. Just helping keep networks operating. But if there’s a lesson I learned from those old-school threats, it’s this:
The weak chain will always be targeted by attackers. If it’s not the perimeter, it’s the keys.

So, yeah, don’t be lazy about keeping your patches up to date. Tighten cluster access. Question the flashy AI tools. And always — always — bear in mind that your encryption is only as good as how effectively you keep your secrets.

Now if you’ll excuse me, I’m going to go make another pot of coffee and possibly stop clicking this key insanity. Although one thing’s for certain, if you are using any Palo Alto clusters with MACsec, do not overlook this.

Stay safe out there,

Sanjay Seth

Cybersecurity Consultant at P J Networks Pvt Ltd

add the image which i have generated and is at a link https://pjnetworks.net/linkedin/114.jpg