Ruby 1.8.5 and earlier, 1.8.6 through 1.8.6-p286, 1.8.7 through 1.8.7-p71, and 1.9 through r18423 does not properly restrict access to critical variables and methods at various safe levels, which allows context-dependent attackers to bypass intended access restrictions via (1) untrace_var, (2) $PROGRAM_NAME, and (3) syslog at safe level 4, and (4) insecure methods at safe levels 1 through 3.
https://www.redhat.com/archives/fedora-package-announce/2008-October/msg00299.html
https://www.redhat.com/archives/fedora-package-announce/2008-October/msg00259.html
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11602
https://exchange.xforce.ibmcloud.com/vulnerabilities/44369
http://www.vupen.com/english/advisories/2009/1297
http://www.vupen.com/english/advisories/2008/2334
http://www.us-cert.gov/cas/techalerts/TA09-133A.html
http://www.securitytracker.com/id?1020656
http://www.securityfocus.com/archive/1/495884/100/0/threaded
http://www.redhat.com/support/errata/RHSA-2008-0897.html
http://www.redhat.com/support/errata/RHSA-2008-0895.html
http://www.debian.org/security/2008/dsa-1652
http://www.debian.org/security/2008/dsa-1651
http://wiki.rpath.com/wiki/Advisories:rPSA-2008-0264
http://support.avaya.com/elmodocs2/security/ASA-2008-424.htm
http://support.apple.com/kb/HT3549
http://security.gentoo.org/glsa/glsa-200812-17.xml
http://secunia.com/advisories/35074
http://secunia.com/advisories/33178
http://secunia.com/advisories/32372
http://secunia.com/advisories/32371
http://secunia.com/advisories/32256
http://secunia.com/advisories/32255
http://secunia.com/advisories/32219
http://secunia.com/advisories/32165
http://secunia.com/advisories/31697
http://secunia.com/advisories/31430
http://lists.apple.com/archives/security-announce/2009/May/msg00002.html