Ruby 1.9.3-p327 was released to correct a hash-flooding DoS vulnerability that only affects 1.9.x and the 2.0.0 preview .
As noted in the upstream report:
Carefully crafted sequence of strings can cause a denial of service attack on the service that parses the sequence to create a Hash object by using the strings as keys. For instance, this vulnerability affects web application that parses the JSON data sent from untrusted entity.
This vulnerability is similar to CVS-2011-4815 for ruby 1.8.7. ruby 1.9 versions were using modified MurmurHash function but it's reported that there is a way to create sequence of strings that collide their hash values each other. This fix changes the Hash function of String object from the MurmurHash to SipHash 2-4.
Ruby 1.8.x is not noted as being affected by this flaw.
The upstream commit is here:
Upstream has confirmed that 1.8.x is not affected by this flaw.
Not vulnerable. This issue did not affect the versions of ruby as shipped with Red Hat Enterprise Linux 5 and 6.
Created ruby tracking bugs for this issue
Affects: fedora-17 [bug 875267]
Affects: fedora-18 [bug 875268]
Fixed in Fedora 17 and 18 via:
This issue has been addressed in following products:
RHEL 6 Version of OpenShift Enterprise
Via RHSA-2013:0582 https://rhn.redhat.com/errata/RHSA-2013-0582.html