libsafe 2.0-11 and earlier allows attackers to bypass protection against format string vulnerabilities via format strings that use the "'" and "I" characters, which are implemented in libc but not libsafe.
The printf wrappers in libsafe 2.0-11 and earlier do not properly handle argument indexing specifiers, which could allow attackers to exploit certain function calls through arguments that are not verified by libsafe.