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Vulnerability of Perl: integer overflow of Regex Backref

Synthesis of the vulnerability 

An attacker can generate an integer overflow in via a back reference in a Perl regular expression, in order to trigger a denial of service, and possibly to execute code.
Vulnerable software: Perl Core, Ubuntu.
Severity of this announce: 2/4.
Creation date: 26/01/2015.
Références of this computer vulnerability: 776046, CVE-2013-7422, USN-2916-1, VIGILANCE-VUL-16051.

Description of the vulnerability 

The Perl language supports regular expressions, with search of patterns already found (backref). The syntax is "\numberOfTheSearchedGroup".

However, if the group number is too large, the atoi() function returns a negative integer, and an invalid memory area is accessed.

An attacker can therefore generate an integer overflow in via a back reference in a Perl regular expression, in order to trigger a denial of service, and possibly to execute code.
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This computer vulnerability alert impacts software or systems such as Perl Core, Ubuntu.

Our Vigil@nce team determined that the severity of this computer threat alert is medium.

The trust level is of type confirmed by the editor, with an origin of document.

A proof of concept or an attack tool is available, so your teams have to process this alert. An attacker with a technician ability can exploit this security vulnerability.

Solutions for this threat 

Perl: version 5.20.
The version 5.20 is fixed:
  http://www.perl.org/

Perl: patch for Regex Backref.
A patch is available in information sources.

Ubuntu: new perl packages.
New packages are available:
  Ubuntu 15.10: perl 5.20.2-6ubuntu0.2
  Ubuntu 14.04 LTS: perl 5.18.2-2ubuntu1.1
  Ubuntu 12.04 LTS: perl 5.14.2-6ubuntu2.5
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