The release of ZF 1.12.12 was just announced, with Security Updates especially on
Zend_Mail and Zend_Http components.
For more information, please read the official release announcement:
Zend Framework 1.12.12 Released
Also, the ZF PEAR channel was updated to latest 1.12.12 release.
pear upgrade zend/zend
We strongly recommend that consumers of the Zend_Http and Zend_Mail components upgrade immediately.
Also, DotKernel Application Framework use intensively the Zend_Mail component.
If you cannot, you can download the patch separately and apply it to your ZF install:
May 20, 2015 EDIT:
Zend Framework 1.12.13 was released, in order to fix a regression issue introduced in 1.12.12 release.