An obsolete weakness occurs when someone uses deprecated or obsolete functions when building a system. As a programming language evolves, some functions occasionally become obsolete.
These functions are considered obsolete on most systems, and very non-portable.
glibc-2.5-20061008T1257/signal/signal.h
The highlighted line of code below is the trigger point of this particular Centos 6 obsolete weakness.
/* Send signal SIG to process number PID. If PID is zero,
send SIG to all processes in the current process's process group.
If PID is < -1, send SIG to all processes in process group - PID. */
#ifdef __USE_POSIX
extern int kill (__pid_t __pid, int __sig) __THROW;
#endif /* Use POSIX. */
#if defined __USE_BSD || defined __USE_XOPEN_EXTENDED
/* Send SIG to all processes in process group PGRP.
If PGRP is zero, send SIG to all processes in
the current process's process group. */
extern int killpg (__pid_t __pgrp, int __sig) __THROW;
#endif /* Use BSD || X/Open Unix. */
__BEGIN_NAMESPACE_STD
/* Raise signal SIG, i.e., send SIG to yourself. */
extern int raise (int __sig) __THROW;
__END_NAMESPACE_STD
#ifdef __USE_SVID
/* SVID names for the same things. */
extern __sighandler_t ssignal (int __sig, __sighandler_t __handler)
__THROW;
extern int gsignal (int __sig) __THROW;
#endif /* Use SVID. */
#ifdef __USE_MISC
/* Print a message describing the meaning of the given signal number. */
extern void psignal (int __sig, __const char *__s);
#endif /* Use misc. */
/* The 'sigpause' function has two different interfaces. The original
BSD definition defines the argument as a mask of the signal, while
the more modern interface in X/Open defines it as the signal
number. We go with the BSD version unless the user explicitly
selects the X/Open version.
This function is a cancellation point and therefore not marked with
__THROW. */
extern int __sigpause (int __sig_or_mask, int __is_sig);
#ifdef __FAVOR_BSD
/* Set the mask of blocked signals to MASK,
wait for a signal to arrive, and then restore the mask. */
extern int sigpause (int __mask) __THROW __attribute_deprecated__;
#else
# ifdef __USE_XOPEN
# ifdef __GNUC__