In Undertow 2.x before 2.0.0.Alpha2, 1.4.x before 1.4.17.Final, and 1.3.x before 1.3.31.Final, it was found that the fix for CVE-2017-2666 was incomplete and invalid characters are still allowed in the query string and path parameters. This could be exploited, in conjunction with a proxy that also permitted the invalid characters but with a different interpretation, to inject data into the HTTP response. By manipulating the HTTP response the attacker could poison a web-cache, perform an XSS attack, or obtain sensitive information from requests other than their own.
access.redhat.com/errata/RHSA-2017:3454
access.redhat.com/errata/RHSA-2017:3455
access.redhat.com/errata/RHSA-2017:3456
access.redhat.com/errata/RHSA-2017:3458
access.redhat.com/errata/RHSA-2018:0002
access.redhat.com/errata/RHSA-2018:0003
access.redhat.com/errata/RHSA-2018:0004
access.redhat.com/errata/RHSA-2018:0005
access.redhat.com/errata/RHSA-2018:1322
bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-7559
issues.jboss.org/browse/UNDERTOW-1251