I pinned the release to 5.3.2-1ubuntu4 and downgraded. This is the core-dump:

Core was generated by `/usr/sbin/apache2 -k start'.
Program terminated with signal 11, Segmentation fault.
#0  0x00007f3168507343 in _zend_mm_free_canary_int (heap=0x7f316e2b8a30, p=0xe781bdf254723a17) at /build/buildd/php5-5.3.2/Zend/zend_alloc_canary.c:2090
2090    /build/buildd/php5-5.3.2/Zend/zend_alloc_canary.c: No such file or directory.
        in /build/buildd/php5-5.3.2/Zend/zend_alloc_canary.c
(gdb) bt
#0  0x00007f3168507343 in _zend_mm_free_canary_int (heap=0x7f316e2b8a30, p=0xe781bdf254723a17) at /build/buildd/php5-5.3.2/Zend/zend_alloc_canary.c:2090
#1  0x00007f31684e693d in _zval_dtor_func (zvalue=0x7f316e4f72a8) at /build/buildd/php5-5.3.2/Zend/zend_variables.c:36
#2  0x00007f31684da9bd in _zval_ptr_dtor (zval_ptr=0x7f316e4f9b68) at /build/buildd/php5-5.3.2/Zend/zend_variables.h:35
#3  0x00007f31684f3642 in zend_hash_apply_deleter (ht=0x7f3168bdea48, p=0x7f316e4f9b50) at /build/buildd/php5-5.3.2/Zend/zend_hash.c:813
#4  0x00007f31684f38c8 in zend_hash_graceful_reverse_destroy (ht=0x7f3168bdea48) at /build/buildd/php5-5.3.2/Zend/zend_hash.c:848
#5  0x00007f31684daf6e in shutdown_executor () at /build/buildd/php5-5.3.2/Zend/zend_execute_API.c:256
#6  0x00007f31684e76d2 in zend_deactivate () at /build/buildd/php5-5.3.2/Zend/zend.c:962
#7  0x00007f3168493385 in php_request_shutdown (dummy=0x7f316e2b8a30) at /build/buildd/php5-5.3.2/main/main.c:1649
#8  0x00007f3168573dc7 in php_handler (r=0x7f3168573dc7) at /build/buildd/php5-5.3.2/sapi/apache2handler/sapi_apache2.c:512
#9  0x00007f316c337140 in ap_run_handler (r=0x7f316e536a68) at /build/buildd/apache2-2.2.14/server/config.c:159
#10 0x00007f316c33aaa8 in ap_invoke_handler (r=0x7f316e536a68) at /build/buildd/apache2-2.2.14/server/config.c:373
#11 0x00007f316c34849c in ap_internal_redirect (new_uri=<value optimized out>, r=<value optimized out>) at /build/buildd/apache2-2.2.14/modules/http/http_request.c:501
#12 0x00007f3165b2fc95 in ?? () from /usr/lib/apache2/modules/mod_rewrite.so
#13 0x00007f316c337140 in ap_run_handler (r=0x7f316e53ca38) at /build/buildd/apache2-2.2.14/server/config.c:159
#14 0x00007f316c33aaa8 in ap_invoke_handler (r=0x7f316e53ca38) at /build/buildd/apache2-2.2.14/server/config.c:373
#15 0x00007f316c348678 in ap_process_request (r=0x7f316e53ca38) at /build/buildd/apache2-2.2.14/modules/http/http_request.c:282
#16 0x00007f316c345528 in ap_process_http_connection (c=0x7f316e525728) at /build/buildd/apache2-2.2.14/modules/http/http_core.c:190
#17 0x00007f316c33ecf8 in ap_run_process_connection (c=0x7f316e525728) at /build/buildd/apache2-2.2.14/server/connection.c:43
#18 0x00007f316c34d037 in child_main (child_num_arg=<value optimized out>) at /build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:662
#19 0x00007f316c34d34a in make_child (s=0x7f316e126938, slot=31) at /build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:758
#20 0x00007f316c34d67b in startup_children (_pconf=<value optimized out>, plog=<value optimized out>, s=<value optimized out>) at /build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:776
#21 ap_mpm_run (_pconf=<value optimized out>, plog=<value optimized out>, s=<value optimized out>) at /build/buildd/apache2-2.2.14/server/mpm/prefork/prefork.c:997
#22 0x00007f316c323350 in main (argc=3, argv=0x7fff4c5330e8) at /build/buildd/apache2-2.2.14/server/main.c:742