pod install returns fatal error: SSL certificate issue?

Github's SSL certificate looks fine from my end, but maybe you have distrusted it for some reason, or you are using a proxy. To resolve:

Using the Safari browser (not Chrome, Firefox or Opera) on Mac OS X 10.9 (Mavericks) visit https://github.com (no www.).

If an alert pops up, press the "Show Certificate" button, check "Always Trust", and then "Continue."

If no alert pops up, press the green or gray Security button by the URL:

Then make sure "Always trust" is checked on the certificate.

If this doesn't resolve your issue, try temporarily disabling any proxy servers you might be running, such as Charles.

After that, pod install should work.

Note: A portion of my answer text was copied from this answer.

Under the hood pod uses just a regular git, so disabling SSL validation for git will solve the problem:

GIT_SSL_NO_VERIFY=true pod install