curl / Docs / Security / IDNA 2003 makes curl use wrong

IDNA 2003 makes curl use wrong host

Project curl Security Advisory, November 2, 2016 - Permalink

VULNERABILITY

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.

curl is not alone with this problem, as there's currently a big flux in the world of network user-agents about which IDNA version to support and use.

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

We are not aware of any exploit of this flaw.

INFO

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2016-8625 to this issue.

AFFECTED VERSIONS

This flaw exists in the following curl versions.

libcurl is used by many applications, but not always advertised as such!

THE SOLUTION

In version 7.51.0, the parser function is fixed.

A patch for CVE-2016-8625 is available.

RECOMMENDATIONS

We suggest you take one of the following actions immediately, in order of preference:

A - Upgrade curl and libcurl to version 7.51.0

B - Apply the patch to your version and rebuild

TIME LINE

It was first reported to the curl project on October 11 by Christian Heimes.

We contacted distros@openwall on October 19.

curl 7.51.0 was released on November 2 2016, coordinated with the publication of this advisory.

CREDITS

Thanks to Christian Heimes