The MITRE CVE dictionary describes this issue as:
fs/proc/base.c in the Linux kernel before 220.127.116.11 does not properly restrict access to /proc/#####/io files, which allows local users to obtain sensitive I/O statistics by polling a file, as demonstrated by discovering the length of another user's password.
Find out more about CVE-2011-2495 from the
MITRE CVE dictionary dictionary and
This has been addressed in Red Hat Enterprise Linux 5, 6 and Red Hat Enterprise MRG via https://rhn.redhat.com/errata/RHSA-2011-1212.html, https://rhn.redhat.com/errata/RHSA-2011-1189.html, and https://rhn.redhat.com/errata/RHSA-2011-1253.html. Red Hat Enterprise Linux 4 is now in Production 3 of the maintenance life-cycle, https://access.redhat.com/support/policy/updates/errata/, therefore the fix for this issue is not currently planned to be included in the future updates.