It was discovered that Undertow before 1.4.17, 1.3.31 and 2.0.0 processes http request headers with unusual whitespaces which can cause possible http request smuggling.
bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-12165
github.com/undertow-io/undertow
github.com/undertow-io/undertow/commit/1e72647818c9fb31b693a953b1ae595a6c82eb7f
github.com/undertow-io/undertow/commit/5b008b7ac312c6cdb76679ff58c43620bb79d44f
github.com/undertow-io/undertow/commit/691440ee58259fba76711b60d56dde6679808bdc
issues.redhat.com/browse/UNDERTOW-1251
nvd.nist.gov/vuln/detail/CVE-2017-12165