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cURL > Docs > Security > Security Advisory June 23 2011

Security Advisory June 23 2011

                   libcurl inappropriate GSSAPI delegation
                   =======================================
 
Project cURL Security Advisory, June 23rd 2011
http://curl.haxx.se/docs/security.html
 
1. VULNERABILITY
 
  When doing GSSAPI authentication, libcurl unconditionally performs
  credential delegation. This hands the server a copy of the client's security
  credentials, allowing the server to impersonate the client to any other
  using the same GSSAPI mechanism. This is obviously a very sensitive
  operation, which should only be done when the user explicitly so directs.
 
  The GSS/Negotiate feature is only used by libcurl for HTTP authentication if
  told to, and only if libcurl was built with a library that provides the
  GSSAPI. Many builds of libcurl don't have GSS enabled.
 
  There is no known exploit for this problem.
 
  The Common Vulnerabilities and Exposures (CVE) project has assigned the name
  CVE-2011-2192 to this issue.
 
2. AFFECTED VERSIONS
 
  Affected versions: curl 7.10.6 to and including 7.21.6
  Not affected versions: curl < 7.10.6 and >= 7.21.7
 
  Also note that libcurl is used by many applications, and not always
  advertised as such.
 
3. THE SOLUTION
 
  libcurl 7.21.7 avoids setting the option that selects delegation.
 
4. RECOMMENDATIONS
 
  We suggest you take one of the following actions immediately, in order of
  preference:
 
  A - Upgrade to curl and libcurl 7.21.7
 
  B - Apply this patch and rebuild libcurl
 
      http://curl.haxx.se/curl-gssapi-delegation.patch
 
  C - Disable credential forwarding. Assuming the GSSAPI mechanism is
      Kerberos, users can acquire an initial credential (TGT) which is not
      forwardable. On Unix platforms, both the MIT and Heimdal versions of
      kinit use the -F flag for this (note the capital "F"; -f does the
      opposite!). You can also set this as a global default in /etc/krb5.conf
      (or wherever that file lives in a particular installation):
 
      [libdefaults]
      forwardable = no
 
  D - Stop using GSS/Negotiate
 
5. TIME LINE
 
  Richard Silverman realized the problem exists and reported it to us on June
  6th 2011.
 
  We discussed solutions and a first patch was written on June 8th.
 
  curl 7.21.7 was released on June 23rd 2011, coordinated with the publication
  of this this flaw.
 
6. CREDITS
 
  Reported to us by Richard Silverman. Thanks a lot!
 
  Daniel Stenberg wrote the primary patch and this advisory. Additional
  help and valuable feedback provided by Dan Fandrich and Julien Chaffraix.

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