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             AUSCERT External Security Bulletin Redistribution

                               ESB-2021.1334
                      USN-4922-1: Ruby vulnerability
                               21 April 2021

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Ruby
Publisher:         Ubuntu
Operating System:  Ubuntu
Impact/Access:     Create Arbitrary Files -- Remote with User Interaction
                   Reduced Security       -- Remote with User Interaction
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-28965  

Reference:         ESB-2021.1285
                   ESB-2021.1147
                   ESB-2021.1145

Original Bulletin: 
   https://ubuntu.com/security/notices/USN-4922-1

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USN-4922-1: Ruby vulnerability
20 April 2021

Ruby incorrectly handled XML documents.
Releases

  o Ubuntu 20.10
  o Ubuntu 20.04 LTS
  o Ubuntu 18.04 LTS
  o Ubuntu 16.04 LTS

Packages

  o ruby2.3 - Object-oriented scripting language
  o ruby2.5 - Object-oriented scripting language
  o ruby2.7 - Object-oriented scripting language

Details

Juho Nurminen discovered that the REXML gem bundled with Ruby incorrectly
parsed and serialized XML documents. A remote attacker could possibly use
this issue to perform an XML round-trip attack.

Update instructions

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

Ubuntu 20.10

  o ruby2.7 - 2.7.1-3ubuntu1.3
  o libruby2.7 - 2.7.1-3ubuntu1.3

Ubuntu 20.04

  o ruby2.7 - 2.7.0-5ubuntu1.4
  o libruby2.7 - 2.7.0-5ubuntu1.4

Ubuntu 18.04

  o ruby2.5 - 2.5.1-1ubuntu1.9
  o libruby2.5 - 2.5.1-1ubuntu1.9

Ubuntu 16.04

  o libruby2.3 - 2.3.1-2~ubuntu16.04.16
  o ruby2.3 - 2.3.1-2~ubuntu16.04.16

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

References

  o CVE-2021-28965

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