According to an advisory from Secunia, the flaw could be exploited to launch code execution attacks with manipulated document files.
From the OpenOffice.org warning:
A security vulnerability in the custom memory allocation function from OpenOffice.org may lead to heap overflows and allow a remote unprivileged user who provides a OpenOffice.org document that is opened by a local user to execute arbitrary commands on the system with the privileges of the user running OpenOffice.org. No working exploit is known right now.
Secunia says the vulnerability is caused due to an integer overflow error in "rtl_allocateMemory()" and can be exploited to cause heap-based buffer overflows via a specially crafted document.