=========================================================================Ubuntu Security Notice USN-4201-1
November 26, 2019

ruby2.3, ruby2.5 vulnerabilities
=========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 19.10
- Ubuntu 19.04
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in Ruby.

Software Description:
- ruby2.5: Interpreter of object-oriented scripting language Ruby
- ruby2.3: Object-oriented scripting language

Details:

It was discovered that Ruby incorrectly handled certain files.
An attacker could possibly use this issue to pass path matching
what can lead to an unauthorized access. (CVE-2019-15845)

It was discovered that Ruby incorrectly handled certain regular expressions.
An attacker could use this issue to cause a denial of service.
(CVE-2019-16201)

It was discovered that Ruby incorrectly handled certain HTTP headers.
An attacker could possibly use this issue to execute arbitrary code.
(CVE-2019-16254)

It was discovered that Ruby incorrectly handled certain inputs.
An attacker could possibly use this issue to execute arbitrary code.
(CVE-2019-16255)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 19.10:
  libruby2.5                      2.5.5-4ubuntu2.1
  ruby2.5                         2.5.5-4ubuntu2.1

Ubuntu 19.04:
  libruby2.5                      2.5.5-1ubuntu1.1
  ruby2.5                         2.5.5-1ubuntu1.1

Ubuntu 18.04 LTS:
  libruby2.5                      2.5.1-1ubuntu1.6
  ruby2.5                         2.5.1-1ubuntu1.6

Ubuntu 16.04 LTS:
  libruby2.3                      2.3.1-2~ubuntu16.04.14
  ruby2.3                         2.3.1-2~ubuntu16.04.14

In general, a standard system update will make all the necessary changes.

References:
  https://ubuntu.com/security/notices/USN-4201-1
  CVE-2019-15845, CVE-2019-16201, CVE-2019-16254, CVE-2019-16255

Package Information:
  https://launchpad.net/ubuntu/+source/ruby2.5/2.5.5-4ubuntu2.1
  https://launchpad.net/ubuntu/+source/ruby2.5/2.5.5-1ubuntu1.1
  https://launchpad.net/ubuntu/+source/ruby2.5/2.5.1-1ubuntu1.6
  https://launchpad.net/ubuntu/+source/ruby2.3/2.3.1-2~ubuntu16.04.14