Trying with Virtualbox "universal" installer (same errors with deb packages)
$ sudo ./VirtualBox-4.3.14-95030-Linux_amd64.run
Verifying archive integrity... All good.
Uncompressing VirtualBox for Linux installation............
VirtualBox Version 4.3.14 r95030 (2014-07-15T16:14:32Z) installer
Installing VirtualBox to /opt/VirtualBox
Python found: python, installing bindings...
Building the VirtualBox kernel modules
ERROR (dkms apport): binary package for vboxhost: 4.3.14 not found
Error! Bad return status for module build on kernel: 3.11.0-26-generic (x86_64)
Consult /var/lib/dkms/vboxhost/4.3.14/build/make.log for more information.

VirtualBox has been installed successfully.

You will find useful information about using VirtualBox in the user manual
  /opt/VirtualBox/UserManual.pdf
and in the user FAQ
  http://www.virtualbox.org/wiki/User_FAQ

We hope that you enjoy using VirtualBox.
-----------------------------------------------------------------------------
In /var/lib/dkms/vboxhost/4.3.14/build/make.log :

DKMS make.log for vboxhost-4.3.14 for kernel 3.11.0-26-generic (x86_64)
mercredi 20 août 2014, 15:50:40 (UTC+0200)
make: entrant dans le répertoire « /usr/src/linux-headers-3.11.0-26-generic »
/usr/src/linux-headers-3.11.0-26-generic/arch/x86/Makefile:113: CONFIG_X86_X32 enabled but no binutils support
  LD      /var/lib/dkms/vboxhost/4.3.14/build/built-in.o
  LD      /var/lib/dkms/vboxhost/4.3.14/build/vboxdrv/built-in.o
  CC [M]  /var/lib/dkms/vboxhost/4.3.14/build/vboxdrv/linux/SUPDrv-linux.o
In file included from /var/lib/dkms/vboxhost/4.3.14/build/vboxdrv/include/iprt/types.h:31:0,
                 from /var/lib/dkms/vboxhost/4.3.14/build/vboxdrv/include/VBox/types.h:30,
                 from /var/lib/dkms/vboxhost/4.3.14/build/vboxdrv/linux/../SUPDrvInternal.h:35,
                 from /var/lib/dkms/vboxhost/4.3.14/build/vboxdrv/linux/SUPDrv-linux.c:31:
/var/lib/dkms/vboxhost/4.3.14/build/vboxdrv/include/iprt/stdarg.h:42:22: erreur fatale: stdarg.h : Aucun fichier ou dossier de ce type
compilation terminée.
make[2]: *** [/var/lib/dkms/vboxhost/4.3.14/build/vboxdrv/linux/SUPDrv-linux.o] Erreur 1
make[1]: *** [/var/lib/dkms/vboxhost/4.3.14/build/vboxdrv] Erreur 2
make: *** [_module_/var/lib/dkms/vboxhost/4.3.14/build] Erreur 2
make: quittant le répertoire « /usr/src/linux-headers-3.11.0-26-generic »
------------------------------------------------------------------------------------------
Trying to rebuild module :
$ sudo /etc/init.d/vboxdrv setup
[sudo] password for fsoyer:
Stopping VirtualBox kernel modules ...done.
Uninstalling old VirtualBox DKMS kernel modules ...done.
Trying to register the VirtualBox kernel modules using DKMSERROR (dkms apport): binary package for vboxhost: 4.3.14 not found
Error! Bad return status for module build on kernel: 3.11.0-26-generic (x86_64)
Consult /var/lib/dkms/vboxhost/4.3.14/build/make.log for more information.
 ...failed!
  (Failed, trying without DKMS)
Recompiling VirtualBox kernel modules ...failed!
  (Look at /var/log/vbox-install.log to find out what went wrong)
-------------------------------------------------------------------
In /var/log/vbox-install.log :

Uninstalling modules from DKMS
  removing old DKMS module vboxhost version  4.3.14

------------------------------
Deleting module version: 4.3.14
completely from the DKMS tree.
------------------------------
Done.
Attempting to install using DKMS

Creating symlink /var/lib/dkms/vboxhost/4.3.14/source ->
                 /usr/src/vboxhost-4.3.14

DKMS: add completed.

Kernel preparation unnecessary for this kernel.  Skipping...

Building module:
cleaning build area....
make KERNELRELEASE=3.11.0-26-generic -C /lib/modules/3.11.0-26-generic/build M=/var/lib/dkms/vboxhost/4.3.14/build....(bad exit status: 2)
Failed to install using DKMS, attempting to install without
make KBUILD_VERBOSE=1 SUBDIRS=/tmp/vbox.0 SRCROOT=/tmp/vbox.0 CONFIG_MODULE_SIG= -C /lib/modules/3.11.0-26-generic/build modules
/usr/src/linux-headers-3.11.0-26-generic/arch/x86/Makefile:113: CONFIG_X86_X32 enabled but no binutils support
test -e include/generated/autoconf.h -a -e include/config/auto.conf || (		\
	echo >&2;							\
	echo >&2 "  ERROR: Kernel configuration is invalid.";		\
	echo >&2 "         include/generated/autoconf.h or include/config/auto.conf are missing.";\
	echo >&2 "         Run 'make oldconfig && make prepare' on kernel src to fix it.";	\
	echo >&2 ;							\
	/bin/false)
mkdir -p /tmp/vbox.0/.tmp_versions ; rm -f /tmp/vbox.0/.tmp_versions/*
make -f scripts/Makefile.build obj=/tmp/vbox.0
  gcc -Wp,-MD,/tmp/vbox.0/linux/.SUPDrv-linux.o.d  -nostdinc -isystem include  -I/usr/src/linux-headers-3.11.0-26-generic/arch/x86/include -Iarch/x86/include/generated  -Iinclude -I/usr/src/linux-headers-3.11.0-26-generic/arch/x86/include/uapi -Iarch/x86/include/generated/uapi -I/usr/src/linux-headers-3.11.0-26-generic/include/uapi -Iinclude/generated/uapi -include /usr/src/linux-headers-3.11.0-26-generic/include/linux/kconfig.h -Iubuntu/include  -D__KERNEL__ -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs -fno-strict-aliasing -fno-common -Werror-implicit-function-declaration -Wno-format-security -fno-delete-null-pointer-checks -O2 -m64 -mno-mmx -mno-sse -mno-red-zone -mcmodel=kernel -maccumulate-outgoing-args -fstack-protector -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -fno-omit-frame-pointer -fno-optimize-sibling-calls -pg -include /tmp/vbox.0/include/VBox/SUPDrvMangling.h -I/lib/modules/3.11.0-26-generic/build/include -I/tmp/vbox.0/ -I/tmp/vbox.0/include -I/tmp/vbox.0/r0drv/linux -I/tmp/vbox.0/vboxdrv/ -I/tmp/vbox.0/vboxdrv/include -I/tmp/vbox.0/vboxdrv/r0drv/linux -D__KERNEL__ -DMODULE -DRT_OS_LINUX -DIN_RING0 -DIN_RT_R0 -DIN_SUP_R0 -DVBOX -DRT_WITH_VBOX -DVBOX_WITH_HARDENING -Wno-declaration-after-statement -DCONFIG_VBOXDRV_AS_MISC -DRT_ARCH_AMD64 -DVBOX_WITH_64_BITS_GUESTS  -DMODULE  -D"KBUILD_STR(s)=#s" -D"KBUILD_BASENAME=KBUILD_STR(SUPDrv_linux)"  -D"KBUILD_MODNAME=KBUILD_STR(vboxdrv)" -c -o /tmp/vbox.0/linux/.tmp_SUPDrv-linux.o /tmp/vbox.0/linux/SUPDrv-linux.c
In file included from /tmp/vbox.0/include/iprt/types.h:31:0,
                 from /tmp/vbox.0/include/VBox/types.h:30,
                 from /tmp/vbox.0/linux/../SUPDrvInternal.h:35,
                 from /tmp/vbox.0/linux/SUPDrv-linux.c:31:
/tmp/vbox.0/include/iprt/stdarg.h:42:22: erreur fatale: stdarg.h : Aucun fichier ou dossier de ce type
compilation terminée.
make[2]: *** [/tmp/vbox.0/linux/SUPDrv-linux.o] Erreur 1
make[1]: *** [_module_/tmp/vbox.0] Erreur 2
make: *** [vboxdrv] Erreur 2