Evolution Data Server provides a unified back-end for applications which interact with contacts, task, and calendar information. Evolution Data Server was originally developed as a back-end for Evolution, but is now used by multiple other applications. Evolution Data Server did not properly check the Secure/Multipurpose Internet Mail Extensions signatures used for public key encryption and signing of e-mail messages. An attacker could use this flaw to spoof a signature by modifying the text of the e-mail message displayed to the user. It was discovered that Evolution Data Server did not properly validate NTLM authentication challenge packets. A malicious server using NTLM authentication could cause an application using Evolution Data Server to disclose portions of its memory or crash during user authentication. Multiple integer overflow flaws which could cause heap-based buffer overflows were found in the Base64 encoding routines used by Evolution Data Server. This could cause an application using Evolution Data Server to crash, or, possibly, execute an arbitrary code when large untrusted data blocks were Base64-encoded. All users of evolution-data-server and evolution28-evolution-data-server are advised to upgrade to these updated packages, which contain backported patches to correct these issues. All running instances of Evolution Data Server and applications using it must be restarted for the update to take effect.