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             AUSCERT External Security Bulletin Redistribution

                               ESB-2021.2339
      CVE-2021-32066: A StartTLS stripping vulnerability in Net::IMAP
                                8 July 2021

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

Product:           Ruby
Publisher:         Ruby
Operating System:  UNIX variants (UNIX, Linux, OSX)
                   Windows
Impact/Access:     Provide Misleading Information -- Unknown/Unspecified
                   Reduced Security               -- Unknown/Unspecified
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-32066  

Reference:         ESB-2021.2337

Original Bulletin: 
   https://www.ruby-lang.org/en/news/2021/07/07/starttls-stripping-in-net-imap/

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CVE-2021-32066: A StartTLS stripping vulnerability in Net::IMAP

Posted by shugo on 7 Jul 2021

A StartTLS stripping vulnerability was discovered in Net::FTP. This
vulnerability has been assigned the CVE identifier CVE-2021-32066 . We strongly
recommend upgrading Ruby.

net-imap is a default gem in Ruby 3.0.1 but it has a packaging issue, so please
upgrade Ruby itself.

Details

Net::IMAP does not raise an exception when StartTLS fails with an unknown
response, which might allow man-in-the-middle attackers to bypass the TLS
protections by leveraging a network position between the client and the
registry to block the StartTLS command, aka a   StartTLS stripping attack.  

Affected Versions

  o Ruby 2.6 series: 2.6.7 and earlier
  o Ruby 2.7 series: 2.7.3 and earlier
  o Ruby 3.0 series: 3.0.1 and earlier

Credits

Thanks to Alexandr Savca for reporting the issue.

History

  o Originally published at 2021-07-07 09:00:00 UTC

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