This just worked for me as well...
I am running 2.3.5 and the error seemed to come on slowly.
meaning that It manifested as my inability to access the cms admin. (however my site, mostly a blog worked fine.)
at first I was being logged out of the cms/admin after a soft time (it would then show this error, but a refresh would let me back to the login screen)
Finally, I can not reach the login screen at all, however the site still runs fine.
The edit listed above has given me access to the cms/admin again.