up to date: 21.3.2017, version 4.2.1 and lower does not receive any updates (probably even security patches?)!
--4.2.x--
4.2.5 beta 4
4.2.4 PL?
4.2.3 PL2
4.2.2 PL6
4.2.1 PL1
4.2.0 PL4
--4.1.x--
4.1.12 PL4
4.1.11 PL3
4.1.10 PL3
4.1.9 PL4
4.1.8 PL4
4.1.7 PL6
4.1.6 PL6
4.1.5 PL7
4.1.4 PL9
4.1.3 PL8
4.1.2 PL8
4.1.1 PL7
4.1.0 PL9
--4.0.x--
4.0.8 PL9
4.0.7 PL7
4.0.6 PL8
4.0.5 PL7
4.0.4 PL8
4.0.3 PL8
4.0.2 PL11
4.0.1 PL7
4.0.0 PL8
Patch Packages are cumulative so you only need the latest one available for your version.
Download: https://members.vbulletin.com/patches.php
vBulletin 3.8.11 requires PHP 5.6.0+ and MySQL 5.5.8+.
vBulletin 3.8.10 requires PHP 5.5.0+ and MySQL 5.0.0+.
vBulletin 3.8.9 requires PHP 5.3.0+ and MySQL 4.1.0+.
vBulletin 3.8.7 and 3.8.8 require PHP 5.2.0+ and MySQL 4.0.16+.
vBulletin 4.2.5 requires PHP 5.6.0+ and MySQL 5.5.8+.
vBulletin 4.2.4 requires PHP 5.5.0+ and MySQL 5.0.0+.
vBulletin 4.2.3 requires PHP 5.4.0+ and MySQL 4.1.0+.
vBulletin 4.2.2 requires PHP 5.2.0+ and MySQL 4.1.0+.
vBulletin 5.2.4+ requires PHP 5.5.0+ and MySQL 5.1.5+.
vBulletin 5.2.4+, 4.2.5+ and 3.8.11+ support PHP 7.0
vBulletin 5.2.6+, 4.2.5+ and 3.8.11+ support PHP 7.1