Arch Linux: Insufficient validation (CVE-2016-8625)

When curl is built with libidn to handle International Domain Names (IDNA), it translates them to puny code for DNS resolving using the IDNA 2003 standard, while IDNA 2008 is the modern and up-to-date IDNA standard. This misalignment causes problems with for example domains using the German ß character (known as the Unicode Character 'LATIN SMALL LETTER SHARP S') which is used at times in the .de TLD and is translated differently in the two IDNA standards, leading to users potentially and unknowingly issuing network transfer requests to the wrong host.

For example, straße.de is translated into strasse.de using IDNA 2003 but is translated into xn--strae-oqa.de using IDNA 2008. Needless to say, those host names could very well resolve to different addresses and be two completely independent servers. IDNA 2008 is mandatory for .de domains.

This name problem exists for DNS-using protocols in curl, but only when built to use libidn.