Tor 0.2.5.12 and 0.2.6.7 fix two security issues that could be used by an attacker to crash hidden services, or crash clients visiting hidden services. Hidden services should upgrade as soon as possible; clients should upgrade whenever packages become available. These releases also contain two simple improvements to make hidden services a bit less vulnerable to denial-of-service attacks. We also made a Tor 0.2.4.27 release so that Debian stable can easily integrate these fixes. The Tor Browser team is currently evaluating whether to put out a new Tor Browser stable release with these fixes, or wait until next week for their scheduled next stable release. (The bugs can introduce hassles for users, but we don't currently view them as introducing any threats to anonymity.) Changes in version 0.2.5.12 - 2015-04-06 Major bugfixes (security, hidden service): Fix an issue that would allow a malicious client to trigger an assertion failure and halt a hidden service. Fixes bug 15600; bugfix on 0.2.1.6-alpha. Reported by "disgleirio". Fix a bug that could cause a client to crash with an assertion failure when parsing a malformed hidden service descriptor. Fixes bug 15601; bugfix on 0.2.1.5-alpha. Found by "DonnchaC". Minor features (DoS-resistance, hidden service): Introduction points no longer allow multiple INTRODUCE1 cells to arrive on the same circuit. This should make it more expensive for attackers to overwhelm hidden services with introductions. Resolves ticket 15515. Changes in version 0.2.6.7 - 2015-04-06 Major bugfixes (security, hidden service): Fix an issue that would allow a malicious client to trigger an assertion failure and halt a hidden service. Fixes bug 15600; bugfix on 0.2.1.6-alpha. Reported by "disgleirio". Fix a bug that could cause a client to crash with an assertion failure when parsing a malformed hidden service descriptor. Fixes bug 15601; bugfix on 0.2.1.5-alpha. Found by "DonnchaC". Minor features (DoS-resistance, hidden service): Introduction points no longer allow multiple INTRODUCE1 cells to arrive on the same circuit. This should make it more expensive for attackers to overwhelm hidden services with introductions. Resolves ticket 15515. Decrease the amount of reattempts that a hidden service performs when its rendezvous circuits fail. This reduces the computational cost for running a hidden service under heavy load. Resolves ticket 11447. Continue reading...
