Bug 1660235 (CVE-2018-19787) - CVE-2018-19787 python-lxml: XSS in lxml.html.clean module in lxml/html/clean.py
Summary: CVE-2018-19787 python-lxml: XSS in lxml.html.clean module in lxml/html/clean.py
Keywords:
Status: CLOSED ERRATA
Alias: CVE-2018-19787
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Red Hat Product Security
QA Contact:
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Whiteboard:
Depends On: 1660236 1660980 1660981 1662779 1662780 1662781 1662782 1662783 1662784 1662785
Blocks: 1660239
TreeView+ depends on / blocked
 
Reported: 2018-12-17 22:20 UTC by Laura Pardo
Modified: 2021-10-27 03:19 UTC (History)
15 users (show)

Fixed In Version: python-lxml 4.2.5
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Environment:
Last Closed: 2021-10-27 03:19:53 UTC
Embargoed:

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Description Laura Pardo 2018-12-17 22:20:55 UTC 
An issue was discovered in lxml before 4.2.5. lxml/html/clean.py in the lxml.html.clean module does not remove javascript: URLs that use escaping, allowing a remote attacker to conduct XSS attacks, as demonstrated by "j a v a s c r i p t:" in Internet Explorer. This is a similar issue to CVE-2014-3146. 


References:
https://github.com/lxml/lxml/commit/6be1d081b49c97cfd7b3fbd934a193b668629109
Comment 1 Laura Pardo 2018-12-17 22:21:07 UTC 
Created python-lxml tracking bugs for this issue:

Affects: fedora-all [bug 1660236]
Comment 2 Scott Gayou 2018-12-19 18:00:41 UTC 
Easy to reproduce. As an example, '<a href="javascrip%20t%20:evil_function()">poc</a>' should be cleaned to '<a href="">poc</a>' but isn't.

Apparently Internet Explorer can somehow execute "j a v a s c r i p t:" (with spaces). I don't have any experience with that, but I'll trust upstream.
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