cURL cURL > Docs > Security > Advisory

Security Advisory March 3 2009

                        libcurl Arbitrary File Access
                        =============================
 
Project cURL Security Advisory, March 3rd 2009
http://curl.haxx.se/docs/security.html
 
1. VULNERABILITY
 
  When told to follow a "redirect" automatically, libcurl does not question
  the new target URL but will follow to any new URL that it understands. As
  libcurl supports FILE:// URLs, a rogue server can thus "trick" a
  libcurl-using application to read a local file instead of the remote one.
 
  This is a problem, for example, when the application is running on a server
  and is written to upload or to otherwise provide the transfered data to a
  user, to another server or to another application etc, as it can be used to
  expose local files it was not meant to.
 
  The problem can also be exploited for uploading, if the rogue server
  redirects the client to a local file and thus it would (over)write a local
  file instead of sending it to the server.
 
  libcurl compiled to support SCP can get tricked to get a file using embedded
  semicolons, which can lead to execution of commands on the given
  server. "Location: scp://name:passwd@host/a'``;date >/tmp/test``;'".
 
  Files on servers other than the one running libcurl are also accessible when
  credentials for those servers are stored in the .netrc file of the user
  running libcurl.  This is most common for FTP servers, but can occur with
  any protocol supported by libcurl.  Files on remote SSH servers are also
  accessible when the user has an unencrypted SSH key.
 
  There is no known exploit at the time of this writing.
 
  The Common Vulnerabilities and Exposures (CVE) project has assigned the name
  CVE-2009-0037 to this issue.
 
2. AFFECTED VERSIONS
 
  Affected versions: curl and libcurl 5.11(!) to and including 7.19.3
  Not affected versions: curl and libcurl 5.10 and earlier, 7.19.4 and later
 
  Also note that (lib)curl is used by many applications, and not always
  advertised as such.
 
3. THE SOLUTION
 
  libcurl 7.19.4 introduces a new option called CURLOPT_REDIR_PROTOCOLS, which
  applications can use to tell libcurl what target protocols automatic
  redirect followings are allowed to use. This will by default exclude FILE
  and SCP URLs.
 
4. RECOMMENDATIONS
 
  We suggest you take one of the following actions immediately, in order of
  preference:
 
  A - Upgrade to curl and libcurl 7.19.4
 
  B - Apply the suitable patch and rebuild
 
    For current CVS HEAD:
    http://curl.haxx.se/CVE-2009-0037/curl-CVSHEAD-CVE-2009-0037.patch
 
    For curl 7.19.0:
    http://curl.haxx.se/CVE-2009-0037/curl-7.19.0-CVE-2009-0037.patch
 
    For curl 7.18.2:
    http://curl.haxx.se/CVE-2009-0037/curl-7.18.2-CVE-2009-0037.patch
 
    For curl 7.18.1:
    http://curl.haxx.se/CVE-2009-0037/curl-7.18.1-CVE-2009-0037.patch
 
    For curl 7.17.0:
    http://curl.haxx.se/CVE-2009-0037/curl-7.17.0-CVE-2009-0037.patch
 
    For curl 7.16.4:
    http://curl.haxx.se/CVE-2009-0037/curl-7.16.4-CVE-2009-0037.patch
 
    For curl 7.15.3:
    http://curl.haxx.se/CVE-2009-0037/curl-7.15.3-CVE-2009-0037.patch
 
    For curl 7.15.1:
    http://curl.haxx.se/CVE-2009-0037/curl-7.15.1-CVE-2009-0037.patch
 
    For curl 7.11.0:
    http://curl.haxx.se/CVE-2009-0037/curl-7.11.0-CVE-2009-0037.patch
 
  C - Disable automatic redirection following in your application and do the
      logic "manually" instead.
 
5. TIME LINE
 
  We were notified by David Kierznowski on Feb 6th, 2009.
 
  We discussed solutions and a first patch was written and tested on Feb 11th.
 
  Vendor-sec was contacted on Feb 12, 2009.
 
  We agreed on and coordinated the synchronous disclosure of this problem
  together with the curl 7.19.4 release.
 
  curl 7.19.4 was released on March 3 2009, just before this flaw was publicly
  disclosed.
 
6. CREDITS
 
  Reported to us by David Kierznowski. Thanks a lot!
 
  Daniel Fandrich researched the issue and helped with the fix.
 
  Michal Marek brought the SCP side of this issue and did a bunch of the
  patch backports.
 
  Daniel Stenberg wrote the primary patch and this advisory.