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CVE-2015-3144

hostname out of boundary memory access

Project curl Security Advisory, April 22 2015 - Permalink

VULNERABILITY

There is a private function in libcurl called fix_hostname() that removes a trailing dot from the hostname if there is one. The function is called after the hostname has been extracted from the URL libcurl has been told to act on.

If a URL is given with a zero-length hostname, like in "http://:80" or just ":80", fix_hostname() indexes the hostname pointer with a -1 offset (as it blindly assumes a non-zero length) and both read and assign that address.

At best, this gets unnoticed but can also lead to a crash or worse. We have not researched further what kind of malicious actions that potentially this could be used for.

INFO

This flaw can also be triggered with the curl command line tool.

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2015-3144 to this issue.

CWE-124: Buffer Underwrite ('Buffer Underflow')

Severity: Medium

AFFECTED VERSIONS

Affected versions: from libcurl 7.37.0 to and including 7.41.0
Not affected versions: libcurl < 7.37.0 and libcurl >= 7.42.0
Introduced-in: https://github.com/curl/curl/commit/5de8d8409

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

SOLUTION

libcurl 7.42.0 better verifies the input string to the affected function.

Fixed-in: https://github.com/curl/curl/commit/0583e87ada7a3cfb10904ae4ab

RECOMMENDATIONS

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

A - Upgrade to curl and libcurl 7.42.0

B - Apply the patch and rebuild libcurl

C - Avoid using URLs with zero-length hostnames!

TIMELINE

It was first reported to the curl project on April 16 2015. We contacted distros@openwall on April 17th.

libcurl 7.42.0 was released on April 22 2015, coordinated with the publication of this advisory.

CREDITS

Reported-by: Hanno Böck
Patched-by: Daniel Stenberg

Thanks a lot!