Tor Browser 10.5a12 is now available from the Tor Browser Alpha download page and also from our

There's a new alpha release available for download. If you build Tor from source, you can download the source code for 0.4.6.1-alpha from the download page on the website. Packages should be available over the coming weeks, with a new alpha Tor Browser release likely next week.

Remember, this is an alpha release: you should only run this if you'd like to find and report more bugs than usual.

Tor 0.4.6.1-alpha is the first alpha release in the 0.4.6.x series. It improves client circuit performance, adds missing features, and improves some of our DoS handling and statistics reporting. It also includes numerous smaller bugfixes.

Below are the changes since 0.4.5.7. (Note that this release DOES include the fixes for the security bugs already fixed in 0.4.5.7.)

Changes in version 0.4.6.1-alpha - 2021-03-18

• Major features (control port, onion services):
  • Add controller support for creating version 3 onion services with client authorization. Previously, only v2 onion services could be created with client authorization. Closes ticket 40084. Patch by Neel Chauhan.
• Major features (directory authorityl):
  • When voting on a relay with a Sybil-like appearance, add the Sybil flag when clearing out the other flags. This lets a relay operator know why their relay hasn't been included in the consensus. Closes ticket 40255. Patch by Neel Chauhan.

We have a new stable release today. If you build Tor from source, you can download the source code for 0.4.5.7 on the download page. Packages should be available within the next several weeks, with a new Tor Browser coming next week.

Also today, Tor 0.3.5.14 (changelog) and Tor 0.4.4.8 (changelog) have also been released; you can find them (and source for older Tor releases) at https://dist.torproject.org.

These releases fix a pair of denial-of-service issues, described below. One of these issues is authority-only.  The other issue affects all Tor instances, and is most damaging on directory authorities and relays.  We recommend that everybody should upgrade to one of these versions once packages are available.

Tor 0.4.5.7 fixes two important denial-of-service bugs in earlier versions of Tor.

One of these vulnerabilities (TROVE-2021-001) would allow an attacker who can send directory data to a Tor instance to force that Tor instance to consume huge amounts of CPU. This is easiest to exploit against authorities, since anybody can upload to them, but directory caches could also exploit this vulnerability against relays or clients when they download. The other vulnerability (TROVE-2021-002) only affects directory authorities, and would allow an attacker to remotely crash the authority with an assertion failure. Patches have already been provided to the authority operators, to help ensure network stability.

We recommend that everybody upgrade to one of the releases that fixes these issues (0.3.5.14, 0.4.4.8, or 0.4.5.7) as they become available to you.

This release also updates our GeoIP data source, and fixes a few smaller bugs in earlier releases.

Changes in version 0.4.5.7 - 2021-03-16

• Major bugfixes (security, denial of service):
  • Disable the dump_desc() function that we used to dump unparseable information to disk. It was called incorrectly in several places, in a way that could lead to excessive CPU usage. Fixes bug 40286; bugfix on 0.2.2.1-alpha. This bug is also tracked as TROVE-2021- 001 and CVE-2021-28089.
  • Fix a bug in appending detached signatures to a pending consensus document that could be used to crash a directory authority. Fixes bug 40316; bugfix on 0.2.2.6-alpha. Tracked as TROVE-2021-002 and CVE-2021-28090.
• Minor features (geoip data):
  • We have switched geoip data sources. Previously we shipped IP-to- country mappings from Maxmind's GeoLite2, but in 2019 they changed their licensing terms, so we were unable to update them after that point. We now ship geoip files based on the IPFire Location Database instead. (See https://location.ipfire.org/ for more information). This release updates our geoip files to match the IPFire Location Database as retrieved on 2021/03/12. Closes ticket 40224.

We invite you to give your feedback in a new user survey.

Tor Browser 10.0.12 is now available from the Tor Browser download page and also from our distribution directory.