CVE-2016-2338: 
Ruby vulnerability analysis and mitigation

CVE-2016-2338 is a heap overflow vulnerability discovered in Ruby's Psych::Emitter start_document function. The vulnerability was initially discovered on June 8, 2015, and publicly disclosed on June 14, 2016. The issue affects Ruby versions 2.2.2 and 2.3.0, where a heap buffer allocation is made based on tags array length, and a specially constructed object passed as an element of the tags array can increase this array size after allocation, leading to a heap overflow (Talos Report).

The vulnerability exists in the Psych::Emitter startdocument function where the heap buffer 'head' allocation is made based on tags array length. The issue occurs when processing the tags array, where each element is checked for tuple format [name,value]. The vulnerability can be triggered when a specially crafted object with a custom 'tostr' method is passed as a name or value in the tuple. This object must have its encoding field set to utf-8 and implement the 'to_str' method. During execution, the method can increase the tags array size after the initial allocation, causing a heap overflow (Talos Report). The vulnerability has received a CVSS score of 9.8 (CRITICAL) with vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (NetApp Advisory).

Successful exploitation of this vulnerability could lead to disclosure of sensitive information, addition or modification of data, or Denial of Service (DoS). The high severity score indicates the potential for significant impact on affected systems (NetApp Advisory).

For Debian 8 'Jessie', this vulnerability has been fixed in version 2.1.5-2+deb8u9. Users are recommended to upgrade their ruby2.1 packages to the patched version (Debian LTS).