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             AUSCERT External Security Bulletin Redistribution

                              ESB-2020.0106.2
           USN-4233-1: GnuTLS update - marking SHA1 as untrusted
                              24 January 2020

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

Product:           GnuTLS
Publisher:         Ubuntu
Operating System:  Ubuntu
                   UNIX variants (UNIX, Linux, OSX)
                   Windows
Impact/Access:     Reduced Security -- Remote/Unauthenticated
Resolution:        Patch/Upgrade

Original Bulletin: 
   https://usn.ubuntu.com/4233-1/
   https://usn.ubuntu.com/4233-2/

Comment: This bulletin contains two (2) Ubuntu security advisories.

Revision History:  January 24 2020: Vendor released advisory USN-4233-2
                   January 10 2020: Initial Release

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USN-4233-1: GnuTLS update
9 January 2020

gnutls28 update
A security issue affects these releases of Ubuntu and its derivatives:

  o Ubuntu 18.04 LTS
  o Ubuntu 16.04 LTS

Summary

SHA1 has been marked as untrusted in GnuTLS.

Software Description

  o gnutls28 - GNU TLS library

Details

As a security improvement, this update marks SHA1 as being untrusted for
digital signature operations.

Update instructions

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

Ubuntu 18.04 LTS
    libgnutls30 - 3.5.18-1ubuntu1.2
Ubuntu 16.04 LTS
    libgnutls30 - 3.4.10-4ubuntu1.6

To update your system, please follow these instructions: https://
wiki.ubuntu.com/Security/Upgrades .

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

References

  o LP: 1858691

- ----------------------------------------------------------------------------


USN-4233-2: GnuTLS update
23 January 2020

gnutls28 update
A security issue affects these releases of Ubuntu and its derivatives:

  o Ubuntu 18.04 LTS
  o Ubuntu 16.04 LTS

Summary

USN-4233-1 marked SHA1 as untrusted in GnuTLS with no workaround.

Software Description

  o gnutls28 - GNU TLS library

Details

USN-4233-1 disabled SHA1 being used for digital signature operations in GnuTLS.
In certain network environments, certificates using SHA1 may still be in use.
This update adds the %VERIFY_ALLOW_BROKEN and %VERIFY_ALLOW_SIGN_WITH_SHA1
priority strings that can be used to temporarily re-enable SHA1 until
certificates can be replaced with a stronger algorithm.

Original advisory details:

As a security improvement, this update marks SHA1 as being untrusted for
digital signature operations.

Update instructions

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

Ubuntu 18.04 LTS
    libgnutls30 - 3.5.18-1ubuntu1.3
Ubuntu 16.04 LTS
    libgnutls30 - 3.4.10-4ubuntu1.7

To update your system, please follow these instructions: https://
wiki.ubuntu.com/Security/Upgrades .

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

References

  o USN-4233-1
  o LP: 1860656

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