Uzbl does anonymous mappings, so PaX will kill it and something similar to this will be logged:

PAX: From 79.144.197.25: execution attempt in: <anonymous mapping>, a0ed8000-a0ee4000 a0ed8000
PAX: terminating task: /usr/bin/uzbl(uzbl):32099, uid/euid: 0/0, PC: a0ed824c, SP: b54af27c
PAX: bytes at PC: 59 89 4f ec c7 07 0a 00 00 00 c7 47 04 0a 00 00 00 c7 47 08 
PAX: bytes at SP-4:

This flags work:

# paxctl -v /usr/bin/uzbl
PaX control v0.5
Copyright 2004,2005,2006,2007 PaX Team <pageexec@freemail.hu>

- PaX flags: P-S--mX-E-R- [/usr/bin/uzbl]
        PAGEEXEC is enabled
        SEGMEXEC is enabled
        MPROTECT is disabled
        RANDEXEC is enabled
        EMUTRAMP is enabled
        RANDMMAP is enabled

Note: for gcc >= 4 then use chpax, for gcc < 4 use paxctl.

This is how to set it up:

# paxctl -PEmRXS /usr/bin/uzbl