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             AUSCERT External Security Bulletin Redistribution

                               ESB-2021.1099
                      USN-4896-1: lxml vulnerability
                               31 March 2021

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

Product:           lxml
Publisher:         Ubuntu
Operating System:  Ubuntu
Impact/Access:     Cross-site Scripting -- Remote with User Interaction
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-28957  

Reference:         ESB-2021.1081
                   ESB-2021.1037

Original Bulletin: 
   https://ubuntu.com/security/notices/USN-4896-1

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USN-4896-1: lxml vulnerability
30 March 2021

lxml could allow cross-site scripting (XSS) attacks.
Releases

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

Packages

  o lxml - pythonic binding for the libxml2 and libxslt libraries

Details

It was discovered that lxml incorrectly handled certain HTML attributes. A
remote attacker could possibly use this issue to perform cross-site
scripting (XSS) attacks.

Update instructions

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

Ubuntu 20.10

  o python3-lxml - 4.5.2-1ubuntu0.4

Ubuntu 20.04

  o python3-lxml - 4.5.0-1ubuntu0.3
  o python-lxml - 4.5.0-1ubuntu0.3

Ubuntu 18.04

  o python3-lxml - 4.2.1-1ubuntu0.4
  o python-lxml - 4.2.1-1ubuntu0.4

Ubuntu 16.04

  o python3-lxml - 3.5.0-1ubuntu0.4
  o python-lxml - 3.5.0-1ubuntu0.4

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

References

  o CVE-2021-28957

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