[arch-security] [ASA-201506-4] curl: information leakage

[Remi Gacogne]

Arch Linux Security Advisory ASA-201506-4
=========================================

Severity: Medium
Date    : 2015-06-22
CVE-ID  : CVE-2015-3236 CVE-2015-3237
Package : curl
Type    : information leakage
Remote  : Yes
Link    : https://wiki.archlinux.org/index.php/CVE

Summary
=======

The package curl before version 7.43.0-1 is vulnerable to information
leakage.

Resolution
==========

Upgrade to 7.43.0-1.

# pacman -Syu "curl>=7.43.0-1"

The problem has been fixed upstream in version 7.43.0.

Workaround
==========

None.

Description
===========

- CVE-2015-3236 (lingering HTTP credentials in connection re-use):

libcurl can wrongly send HTTP credentials when re-using connections.

libcurl allows applications to set credentials for the upcoming transfer
with HTTP Basic authentication, like with CURLOPT_USERPWD for example.
Name and password. Just like all other libcurl options the credentials
are sticky and are kept associated with the "handle" until something is
made to change the situation.

Further, libcurl offers a curl_easy_reset() function that resets a
handle back to its pristine state in terms of all settable options. A
reset is of course also supposed to clear the credentials. A reset is
typically used to clear up the handle and prepare it for a new, possibly
unrelated, transfer.

Within such a handle, libcurl can also store a set of previous
connections in case a second transfer is requested to a host name for
which an existing connection is already kept alive.

With this flaw present, using the handle even after a reset would make
libcurl accidentally use those credentials in a subsequent request if
done to the same host name and connection as was previously accessed.

An example case would be first requesting a password protected resource
from one section of a web site, and then do a second request of a public
resource from a completely different part of the site without
authentication. This flaw would then inadvertently leak the credentials
in the second request.

- CVE-2015-3237 (SMB send off unrelated memory contents):

libcurl can get tricked by a malicious SMB server to send off data it
did not intend to.

In libcurl's state machine function handling the SMB protocol
(smb_request_state()), two length and offset values are extracted from
data that has arrived over the network, and those values are
subsequently used to figure out what data range to send back.

The values are used and trusted without boundary checks and are just
assumed to be valid. This allows carefully handcrafted packages to trick
libcurl into responding and sending off data that was not intended. Or
just crash if the values cause libcurl to access invalid memory.

Impact
======

A passive remote adversary or a malicious HTTP server may be able to
gather sensitive HTTP credentials. A malicious SMB server may be able to
extract arbitrary memory content from a vulnerable SMB client using
libcurl.

References
==========

http://curl.haxx.se/docs/adv_20150617A.html
http://curl.haxx.se/docs/adv_20150617B.html
https://access.redhat.com/security/cve/CVE-2015-3236
https://access.redhat.com/security/cve/CVE-2015-3237

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