Tor before 0.2.4.23 and 0.2.5 before 0.2.5.6-alpha maintains a circuit after an inbound RELAYEARLY cell is received by a client, which makes it easier for remote attackers to conduct traffic-confirmation attacks by using the pattern of RELAY and RELAYEARLY cells as a means of communicating information about hidden service names.

It was reported [1],[2] that Tor suffered from a denial of service vulnerability due to an error when handling SENDME cells. This could be exploited to cause excessive consumption of memory resources within an entry node.

This is fixed in upstream version 0.2.3.25 (git [3]).

[1] https://secunia.com/advisories/51329/ [2] https://trac.torproject.org/projects/tor/ticket/6252 [3] https://gitweb.torproject.org/arma/tor.git/commitdiff/b9b54568c0bb64c32bd0b362954bdbc8c1234b16

Tor before 0.2.3.23-rc allows remote attackers to cause a denial of service (assertion failure and daemon exit) via a renegotiation attempt that occurs after the initiation of the V3 link protocol.

Tor before 0.2.3.24-rc allows remote attackers to cause a denial of service (assertion failure and daemon exit) by performing link protocol negotiation incorrectly.