CVE 2016-2216
The HTTP header parsing code in Node.js 0.10.x before 0.10.42, 0.11.6 through 0.11.16, 0.12.x before 0.12.10, 4.x before 4.3.0, and 5.x before 5.6.0 allows remote attackers to bypass an HTTP response-splitting protection mechanism via UTF-8 encoded Unicode characters in the HTTP header, as demonstrated by %c4%8d%c4%8a.
See the 
CVE page on Mitre.org
for more details.
