Hello!

There are new security releases today. These releases fix four security issues discovered by Jann Horn and Sergei Glazunov at Google's Project Zero.

You can find these releases in the usual place at https://dist.torproject.org. Make sure (as usual) to check the signatures: my key is available at key.cgi?fingerprint=2133BC600AB133E1D826D173FE43009C4607B1FB

Also of note: * The 0.4.6.5 release is the first stable release in its series. * Tomorrow is end-of-life for the 0.4.4.x series; there will be no more 0.4.4.x releases after today.

For information about how long each series will be supported, see https://gitlab.torproject.org/tpo/core/team/-/wikis/NetworkTeam/CoreTorRelea... .

The security issues are as follows. My recommendation is that nobody should freak out, but everybody should upgrade.

o Major bugfixes (security): - Don't allow relays to spoof RELAY_END or RELAY_RESOLVED cell on half-closed streams. Previously, clients failed to validate which hop sent these cells: this would allow a relay on a circuit to end a stream that wasn't actually built with it. Fixes bug 40389; bugfix on 0.3.5.1-alpha. This issue is also tracked as TROVE-2021- 003 and CVE-2021-34548.

o Major bugfixes (security, defense-in-depth): - Detect more failure conditions from the OpenSSL RNG code. Previously, we would detect errors from a missing RNG implementation, but not failures from the RNG code itself. Fortunately, it appears those failures do not happen in practice when Tor is using OpenSSL's default RNG implementation. Fixes bug 40390; bugfix on 0.2.8.1-alpha. This issue is also tracked as TROVE-2021-004. Reported by Jann Horn at Google's Project Zero.

o Major bugfixes (security, denial of service): - Resist a hashtable-based CPU denial-of-service attack against relays. Previously we used a naive unkeyed hash function to look up circuits in a circuitmux object. An attacker could exploit this to construct circuits with chosen circuit IDs, to create collisions and make the hash table inefficient. Now we use a SipHash construction here instead. Fixes bug 40391; bugfix on 0.2.4.4-alpha. This issue is also tracked as TROVE-2021-005 and CVE-2021-34549. Reported by Jann Horn from Google's Project Zero. - Fix an out-of-bounds memory access in v3 onion service descriptor parsing. An attacker could exploit this bug by crafting an onion service descriptor that would crash any client that tried to visit it. Fixes bug 40392; bugfix on 0.3.0.1-alpha. This issue is also tracked as TROVE-2021-006 and CVE-2021-34550. Reported by Sergei Glazunov from Google's Project Zero.

For complete ChangeLogs for each release, see:

https://gitweb.torproject.org/tor.git/tree/ChangeLog?h=tor-0.3.5.15 https://gitweb.torproject.org/tor.git/tree/ChangeLog?h=tor-0.4.4.9 https://gitweb.torproject.org/tor.git/tree/ChangeLog?h=tor-0.4.5.9 https://gitweb.torproject.org/tor.git/tree/ChangeLog?h=tor-0.4.6.5

For the ReleaseNotes for the 0.4.6.x series as a whole, see:

https://gitweb.torproject.org/tor.git/tree/ReleaseNotes?h=tor-0.4.6.5

I'll send out announcements after the download page has updated.

best wishes,