CVE Request: PHP: several issues fixed with 7.0.6, 5.6.21 and 5.5.35

[Salvatore Bonaccorso <carnil () debian org>]

Hi,

With the 7.0.6, 5.6.21 and 5.5.35 PHP releases several issues were
fixed, of those at least those four were as well commited to 5.5.35
(only in security-fixes mode) and might warrant a CVE:

1/ bcpowmod accepts negative scale and corrupts _one_ definition
   - https://bugs.php.net/bug.php?id=72093
   - https://git.php.net/?p=php-src.git;a=commit;h=d650063a0457aec56364e4005a636dc6c401f9cd

2/ xml_parse_into_struct segmentation fault
   - https://bugs.php.net/bug.php?id=72099
   - https://git.php.net/?p=php-src.git;a=commit;h=dccda88f27a084bcbbb30198ace12b4e7ae961cc

3/ Out-of-bounds reads in zif_grapheme_stripos with negative offset
   - https://bugs.php.net/bug.php?id=72061
   - https://git.php.net/?p=php-src.git;a=commit;h=fd9689745c44341b1bd6af4756f324be8abba2fb

4/ Out of bounds heap read access in exif header processing
   - https://bugs.php.net/bug.php?id=72094
   - https://git.php.net/?p=php-src.git;a=commit;h=082aecfc3a753ad03be82cf14f03ac065723ec92

I merely only have checked the php changelogs, but cannot give
background on the impact of those.

Regards,
Salvatore