Daniel Stenberg reported the following vulnerability in cURL:
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,
CURLOPT_MAXCONNECTS and CURLMOPT_MAX_HOST_CONNECTIONS (if using curl_multi
This will be corrected in upstream libcurl and curl 7.35.0.
Red Hat would like to thank the cURL project for reporting this issue. Upstream acknowledges Paras Sethia as the original reporter and Yehezkel Horowitz for discovering the security impact.
This is corrected upstream:
fixed in curl-7.35.0-1.fc21
This affects libcurl 7.10.6 to and including 7.34.0. It is fixed in version 7.35.0.
Created curl tracking bugs for this issue:
Affects: fedora-all [bug 1059327]
curl-7.32.0-4.fc20 has been pushed to the Fedora 20 stable repository. If problems still persist, please make note of it in this bug report.
curl-7.29.0-13.fc19 has been pushed to the Fedora 19 stable repository. If problems still persist, please make note of it in this bug report.
Avoid using HTTP NTLM in your application. If you must use NTLM authentication, ensure that it is the only requested authentication method (use --ntlm specifically, do not use --anyauth or other authentication methods).
This issue has been addressed in following products:
Red Hat Enterprise Linux 6
Via RHSA-2014:0561 https://rhn.redhat.com/errata/RHSA-2014-0561.html
This issue affects the version of curl as shipped with Red Hat Enterprise Linux 5 and 7. The Red Hat Security Response Team has rated this issue as having Moderate security impact, a future update may address this flaw.