With latest stable release 4.4.2 I still get:

$ pwd
/tmp/bug
$ ls -dl
d-wx--x--x 2 paul users 40 Apr  6 09:30 .
$ find /tmp -exec echo '{}' ';'
find: pred.c:1932: launch: Assertion `starting_desc >= 0' failed.
Aborted (core dumped)

As you stated, seems to be fixed in the development branch 4.5.x.

Thanks.

Sorry forget used environments on which reproduced:
- Up to date Arch Linux: find 4.4.2, sudo 1.8.13
- Up to date Ubuntu 14.04: find 4.4.2, sudo 1.8.9p5

My version is from last January: 4.4.2-7 in Ubuntu 14.04 which is still the latest for the distro. I've had this issue for over a year, but now cannot replicate it either. I didn't update findutils, but something had to have changed. I checked that soo many times before submitting this bug.

Thanks for checking it out. If the original reporter can't replicate, then I don't think there is anything else to do but to close this bug.

from my home directoy this works:
sudo -u www-data find /var/www/ -type d ! -perm -070
this does not:
sudo -u www-data find /var/www/ -type d ! -perm -070 -exec chmod 770 {} \;
failure message: find: pred.c:1932: launch: Assertion `starting_desc >= 0' failed.

That same command works fine if I cd to / or /var/www.