perl - security update

Multiple vulnerabilities were discovered in the implementation of the
Perl programming language. The Common Vulnerabilities and Exposures
project identifies the following problems:

• CVE-2016-1238
  John Lightsey and Todd Rinaldo reported that the opportunistic
  loading of optional modules can make many programs unintentionally
  load code from the current working directory (which might be changed
  to another directory without the user realising) and potentially
  leading to privilege escalation, as demonstrated in Debian with
  certain combinations of installed packages.

The problem relates to Perl loading modules from the includes
directory array (“@INC”) in which the last element is the current
directory (“.”). That means that, when perl wants to load a module
(during first compilation or during lazy loading of a module in run
time), perl will look for the module in the current directory at the
end, since ‘.’ is the last include directory in its array of include
directories to seek. The issue is with requiring libraries that are
in “.” but are not otherwise installed.

With this update several modules which are known to be vulnerable
are updated to not load modules from current directory.

Additionally the update allows configurable removal of “.” from @INC
in /etc/perl/sitecustomize.pl for a transitional period. It is
recommended to enable this setting if the possible breakage for a
specific site has been evaluated. Problems in packages provided in
Debian resulting from the switch to the removal of ‘.’ from @INC
should be reported to the Perl maintainers at
[email protected] .

It is planned to switch to the default removal of ‘.’ in @INC in a
subsequent update to perl via a point release if possible, and in
any case for the upcoming stable release Debian 9 (stretch).

• CVE-2016-6185
  It was discovered that XSLoader, a core module from Perl to
  dynamically load C libraries into Perl code, could load shared
  library from incorrect location. XSLoader uses caller() information
  to locate the .so file to load. This can be incorrect if
  XSLoader::load() is called in a string eval. An attacker can take
  advantage of this flaw to execute arbitrary code.

For the stable distribution (jessie), these problems have been fixed in
version 5.20.2-3+deb8u6. Additionally this update includes the
following updated packages to address optional module loading
vulnerabilities related to CVE-2016-1238,
or to address build failures which occur when ‘.’ is removed from @INC:

• cdbs 0.4.130+deb8u1
• debhelper 9.20150101+deb8u2
• devscripts 2.15.3+deb8u12
• exim4 4.84.2-2+deb8u12
• libintl-perl 1.23-1+deb8u12
• libmime-charset-perl 1.011.1-1+deb8u22
• libmime-encwords-perl 1.014.3-1+deb8u12
• libmodule-build-perl 0.421000-2+deb8u12
• libnet-dns-perl 0.81-2+deb8u12
• libsys-syslog-perl 0.33-1+deb8u12
• libunicode-linebreak-perl 0.0.20140601-2+deb8u22

We recommend that you upgrade your perl packages.