I have Console open on my Mac (latest OS X El Capitan) and this error keeps reappearing a few times every second.

4/19/16 1:15:18.021 AM com.apple.kextd[47]: ERROR: invalid signature for com.cisco.kext.acsock, will not load

Does anyone know what exactly this means, and is it a bad thing? It keeps appearing at least a couple of times every second, so it's very persistent. I couldn't find much on this error.

Is it something that can be fixed easily?

2 Answers 2


I had the same issue. kextd was consistently using around 14% CPU and tailing of /var/log/system.log showed that it was trying and failing to load com.cisco.kext.acsock over and over again.

I uninstalled the Cisco AnyConnect VPN client using its installer caused the problem to end immediately.

I suspect I had an old version of AnyConnect installed that was from the pre-El Capitan days, and hence it didn't have a valid the signature. Luckily I don't need the AnyConnect client (I had installed it a while back briefly for some troubleshooting) since I use the built-in client.


This error is shown, because right now every kext (Kernel Extension) must be signed with the developer certificate. Here you can find more info:

A kernel extension, or kext, is a bundle that extends the kernel. With System Integrity Protection, kernel extensions must be signed with a Developer ID for Signing Kexts certificate, and installed into the /Library/Extensions directory.

As of OS X El Capitan, the kext-dev-mode boot-arg is now obsolete.

So in order to get rid of this error you have to get the new kext somehow (maybe Cico has made newer version of its software), or sign this kext by yourself (whih is not so simple).

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