Multiple vulnerabilities have been identified and fixed in ruby:

Cross-site scripting (XSS) vulnerability in the WEBrick HTTP server
in Ruby allows remote attackers to inject arbitrary web script or HTML
via a crafted URI that triggers a UTF-7 error page (CVE-2010-0541).

The FileUtils.remove_entry_secure method in Ruby allows local users
to delete arbitrary files via a symlink attack (CVE-2011-1004).

The safe-level feature in Ruby allows context-dependent attackers
to modify strings via the Exception#to_s method, as demonstrated by
changing an intended pathname (CVE-2011-1005).

The VpMemAlloc function in bigdecimal.c in the BigDecimal class in
Ruby does not properly allocate memory, which allows context-dependent
attackers to execute arbitrary code or cause a denial of service
(application crash) via vectors involving creation of a large
BigDecimal value within a 64-bit process, related to an integer
truncation issue. (CVE-2011-0188).

Packages for 2009.0 are provided as of the Extended Maintenance
Program. Please visit this link to learn more:
http://store.mandriva.com/product_info.php?cPath=149&products_id=490

The updated packages have been patched to correct this issue.