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ESB-2014.1283 - [Win][UNIX/Linux][Debian] tor: Multiple vulnerabilities

Date: 01 August 2014

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Click here for PGP verifiable version
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===========================================================================
             AUSCERT External Security Bulletin Redistribution

                               ESB-2014.1283
                            tor security update
                               1 August 2014

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           tor
Publisher:         Debian
Operating System:  Debian GNU/Linux 7
                   UNIX variants (UNIX, Linux, OSX)
                   Windows
Impact/Access:     Access Privileged Data -- Remote/Unauthenticated
                   Reduced Security       -- Remote/Unauthenticated
Resolution:        Patch/Upgrade
CVE Names:         CVE-2014-5117  

Original Bulletin: 
   http://www.debian.org/security/2014/dsa-2993

Comment: This advisory references vulnerabilities in products which run on 
         platforms other than Debian. It is recommended that administrators 
         running tor check for an updated version of the software for their 
         operating system.

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- - -------------------------------------------------------------------------
Debian Security Advisory DSA-2993-1                   security@debian.org
http://www.debian.org/security/                           Peter Palfrader
July 31, 2014                          http://www.debian.org/security/faq
- - -------------------------------------------------------------------------

Package        : tor
CVE ID         : CVE-2014-5117

Several issues have been discovered in Tor, a connection-based
low-latency anonymous communication system, resulting in information
leaks.

o  Relay-early cells could be used by colluding relays on the network to
   tag user circuits and so deploy traffic confirmation attacks
   [CVE-2014-5117].  The updated version emits a warning and drops the
   circuit upon receiving inbound relay-early cells, preventing this
   specific kind of attack.  Please consult the following advisory for
   more details about this issue:

     https://blog.torproject.org/blog/tor-security-advisory-relay-early-traffic-confirmation-attack

o  A bug in the bounds-checking in the 32-bit curve25519-donna
   implementation could cause incorrect results on 32-bit
   implementations when certain malformed inputs were used along with a
   small class of private ntor keys.  This flaw does not currently
   appear to allow an attacker to learn private keys or impersonate a
   Tor server, but it could provide a means to distinguish 32-bit Tor
   implementations from 64-bit Tor implementations.

The following additional security-related improvements have been
implemented:

o  As a client, the new version will effectively stop using CREATE_FAST
   cells.  While this adds computational load on the network, this
   approach can improve security on connections where Tor's circuit
   handshake is stronger than the available TLS connection security
   levels.

o  Prepare clients to use fewer entry guards by honoring the consensus
   parameters.  The following article provides some background:

     https://blog.torproject.org/blog/improving-tors-anonymity-changing-guard-parameters

For the stable distribution (wheezy), these problems have been fixed in
version 0.2.4.23-1~deb7u1.

For the testing distribution (jessie) and the unstable distribution
(sid), these problems have been fixed in version 0.2.4.23-1.

For the experimental distribution, these problems have been fixed in
version 0.2.5.6-alpha-1.

We recommend that you upgrade your tor packages.

Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at: http://www.debian.org/security/

Mailing list: debian-security-announce@lists.debian.org
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This security bulletin is provided as a service to AusCERT's members.  As
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===========================================================================
Australian Computer Emergency Response Team
The University of Queensland
Brisbane
Qld 4072

Internet Email: auscert@auscert.org.au
Facsimile:      (07) 3365 7031
Telephone:      (07) 3365 4417 (International: +61 7 3365 4417)
                AusCERT personnel answer during Queensland business hours
                which are GMT+10:00 (AEST).
                On call after hours for member emergencies only.
===========================================================================
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