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[SECURITY ADVISORY] re-use of wrong HTTP NTLM connection

From: Daniel Stenberg <>
Date: Wed, 29 Jan 2014 08:23:06 +0100 (CET)

Hi friends,

Synchronized with the 7.35.0 release, we unfortunately also announce the
existence of a security problem in older versions of libcurl.

Web version is here:

The full text follows...

                  libcurl re-use of wrong HTTP NTLM connection

Project cURL Security Advisory, January 29th 2014


   libcurl can in some circumstances re-use the wrong connection when asked to
   do an NTLM-authenticated HTTP or HTTPS request.

   libcurl features a pool of recent connections so that subsequent requests
   can re-use an existing connection to avoid overhead.

   When re-using a connection a range of criterion must first be met. Due to a
   logical error in the code, a request that was issued by an application could
   wrongfully re-use an existing connection to the same server that was
   authenticated using different credentials. One underlying reason being that
   NTLM authenticates connections and not requests, contrary to how HTTP is
   designed to work and how other authentication methods work.

   An application that allows NTLM and another auth method (the bug only
   triggers if more than one auth method is asked for) to a server (that
   responds wanting NTLM) with user1:password1 and then does another operation
   to the same server with user2:password2 (when the previous connection was
   left alive) - the second request will re-use the same connection and since
   it'll then see that the NTLM negotiation is already made, it will just send
   the request over that connection thinking it uses 'user2' credentials when
   it is in fact still using the connection authenticated for user1...

   The set of auth methods to use is set with CURLOPT_HTTPAUTH.

   Two common auth defines in libcurl are CURLAUTH_ANY and CURLAUTH_ANYSAFE.
   Both of them ask for NTLM and other methods and can therefore trigger this

   Applications can disable libcurl's re-use of connections and thus mitigate
   this problem, by using one of the following libcurl options to alter how
   connections are or aren't re-used: CURLOPT_FRESH_CONNECT,

   The Common Vulnerabilities and Exposures (CVE) project has assigned the name
   CVE-2014-0015 to this issue.


   This flaw has existed ever since libcurl started to support NTLM, although
   the code has been restructured a few times over the years so the mistake has
   altered shape over the years.

   Affected versions: from libcurl 7.10.6 to and including 7.34.0
   Not affected versions: libcurl before 7.10.6 and >= 7.35.0

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


   libcurl 7.35.0 makes sure that connections that may use NTLM cannot re-use
   another NTLM-using connection unless the credentials match.

   A patch for this problem (that applies to libcurl >= 7.28.0) is
   available at:

   A patch that applies for 7.27.0 is available at:

   This fix is already committed to the public source code repository because
   the full security impact wasn't properly realized until after the fact.


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

   A - Upgrade to curl and libcurl 7.35.0

   B - Apply the patch and rebuild libcurl

   C - Avoid using HTTP NTLM in your application, or make sure to *only*
       specify NTLM as the requested authentication method.


   It was reported to the curl project on January 7th 2014. We contacted
   distros_at_openwall on January 14th.

   libcurl 7.35.0 was released on January 29th 2014, coordinated with the
   publication of this advisory.


   Bug originally reported by Paras Sethia. The security impact of it was
   flagged by Yehezkel Horowitz.

   Thanks a lot!

List admin:
Received on 2014-01-29