A rack-cors security update has been released for Ubuntu Linux 16.04 LTS.

USN-4571-1: rack-cors vulnerability

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Ubuntu Security Notice USN-4571-1
October 05, 2020

ruby-rack-cors vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 16.04 LTS

Summary:

rack-cors would allow unintended access to files over the network.

Software Description:
- ruby-rack-cors: provides support for Cross-Origin Resource Sharing (CORS) for
Rack compatible web applications

Details:

It was discovered that rack-cors did not properly handle relative file
paths. An attacker could use this vulnerability to access arbitrary files.

Update instructions:

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

Ubuntu 16.04 LTS:
ruby-rack-cors 0.4.0-1+deb9u2build0.16.04.1

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

References:
  https://usn.ubuntu.com/4571-1
CVE-2019-18978

Package Information:
  https://launchpad.net/ubuntu/+source/ruby-rack-cors/0.4.0-1+deb9u2build0.16.04.1