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 [1]. 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. [1] http://www.ruby-lang.org/en/news/2012/11/09/ruby19-hashdos-cve-2012-5371/
The upstream commit is here: http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=37600
Upstream has confirmed that 1.8.x is not affected by this flaw. Statement: 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]
Other references: [2] http://www.openwall.com/lists/oss-security/2012/11/23/4 [3] http://www.ocert.org/advisories/ocert-2012-001.html [4] http://2012.appsec-forum.ch/conferences/#c17 [5] https://www.131002.net/data/talks/appsec12_slides.pdf [6] http://asfws12.files.wordpress.com/2012/11/asfws2012-jean_philippe_aumasson-martin_bosslet-hash_flooding_dos_reloaded.pdf
Fixed in Fedora 17 and 18 via: ruby-1.9.3.327-19.fc17 ruby-1.9.3.327-22.fc18
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