[tor-announce] New stable Tor releases:,, and

Nick Mathewson nickm at torproject.org
Wed Mar 18 16:26:24 UTC 2020


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Source code for Tor is now available; you can download the
source code from the download place on the website. Packages should be
available within the next several days, including a new Tor browser

(For source code for and , see
https://dist.torproject.org/  . There is also a new alpha release
today, but those are announced on the tor-talk@ mailing list.)

These releases fix a couple of denial-of-service vulnerabilities.
Everybody running an older version should upgrade as packages become

Below is the full changelog for  You can find the changelogs
for the other releases at: https://gitweb.torproject.org/tor.git/tree/ChangeLog?h=tor- https://gitweb.torproject.org/tor.git/tree/ChangeLog?h=tor-

Changes in version - 2020-03-18
  This is the third stable release in the 0.4.2.x series. It backports
  numerous fixes from later releases, including a fix for TROVE-2020-
  002, a major denial-of-service vulnerability that affected all
  released Tor instances since Using this vulnerability,
  an attacker could cause Tor instances to consume a huge amount of CPU,
  disrupting their operations for several seconds or minutes. This
  attack could be launched by anybody against a relay, or by a directory
  cache against any client that had connected to it. The attacker could
  launch this attack as much as they wanted, thereby disrupting service
  or creating patterns that could aid in traffic analysis. This issue
  was found by OSS-Fuzz, and is also tracked as CVE-2020-10592.

  We do not have reason to believe that this attack is currently being
  exploited in the wild, but nonetheless we advise everyone to upgrade
  as soon as packages are available.

  o Major bugfixes (security, denial-of-service, backport from
    - Fix a denial-of-service bug that could be used by anyone to
      consume a bunch of CPU on any Tor relay or authority, or by
      directories to consume a bunch of CPU on clients or hidden
      services. Because of the potential for CPU consumption to
      introduce observable timing patterns, we are treating this as a
      high-severity security issue. Fixes bug 33119; bugfix on Found by OSS-Fuzz. We are also tracking this issue
      as TROVE-2020-002 and CVE-2020-10592.

  o Major bugfixes (circuit padding, memory leak, backport from
    - Avoid a remotely triggered memory leak in the case that a circuit
      padding machine is somehow negotiated twice on the same circuit.
      Fixes bug 33619; bugfix on Found by Tobias Pulls.
      This is also tracked as TROVE-2020-004 and CVE-2020-10593.

  o Major bugfixes (directory authority, backport from
    - Directory authorities will now send a 503 (not enough bandwidth)
      code to clients when under bandwidth pressure. Known relays and
      other authorities will always be answered regardless of the
      bandwidth situation. Fixes bug 33029; bugfix on

  o Minor features (continuous integration, backport from
    - Stop allowing failures on the Travis CI stem tests job. It looks
      like all the stem hangs we were seeing before are now fixed.
      Closes ticket 33075.

  o Minor bugfixes (bridges, backport from
    - Lowercase the configured value of BridgeDistribution before adding
      it to the descriptor. Fixes bug 32753; bugfix on

  o Minor bugfixes (logging, backport from
    - If we encounter a bug when flushing a buffer to a TLS connection,
      only log the bug once per invocation of the Tor process.
      Previously we would log with every occurrence, which could cause
      us to run out of disk space. Fixes bug 33093; bugfix

  o Minor bugfixes (onion services v3, backport from
    - Fix an assertion failure that could result from a corrupted
      ADD_ONION control port command. Found by Saibato. Fixes bug 33137;
      bugfix on This issue is also tracked
      as TROVE-2020-003.

  o Minor bugfixes (rust, build, backport from
    - Fix a syntax warning given by newer versions of Rust that was
      creating problems for our continuous integration. Fixes bug 33212;
      bugfix on

  o Testing (Travis CI, backport from
    - Remove a redundant distcheck job. Closes ticket 33194.
    - Sort the Travis jobs in order of speed: putting the slowest jobs
      first takes full advantage of Travis job concurrency. Closes
      ticket 33194.
    - Stop allowing the Chutney IPv6 Travis job to fail. This job was
      previously configured to fast_finish (which requires
      allow_failure), to speed up the build. Closes ticket 33195.
    - When a Travis chutney job fails, use chutney's new "diagnostics.sh"
      tool to produce detailed diagnostic output. Closes ticket 32792.

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