USN-5036-1: Tor vulnerabilities

Releases

• Ubuntu 20.04 LTS
• Ubuntu 18.04 ESM
• Ubuntu 16.04 ESM
• Ubuntu 14.04 ESM

Packages

• tor - anonymizing overlay network for TCP

Details

It was discovered that Tor incorrectly handled certain memory operations. A
remote attacker could use this issue to cause a denial of service. This issue
only affected Ubuntu 18.04 ESM. (CVE-2019-8955)

It was discovered that Tor did not properly handle the input length to
dump_desc() function. A remote attacker could use this issue to cause a denial
of service. This issue only affected Ubuntu 16.04 ESM, Ubuntu 18.04 ESM and
Ubuntu 20.04 ESM. (CVE-2021-28089)

It was discovered that Tor did not properly sanitize the relay nickname in
dirvote_add_signatures_to_pending_consensus() function. An attacker could
possibly use this issue to cause an assertion failure and then cause a denial
of service. (CVE-2021-28090)

It was discovered that Tor did not properly validate the layer hint on
half-open streams. A remote attacker could possibly use this issue to bypass
the access control, leading to remote code execution. This issue only affected
Ubuntu 20.04 ESM. (CVE-2021-34548)

It was discovered that Tor was using an insecure hash function. A remote
attacker could use this issue to cause a denial of service. This issue only
affected Ubuntu 16.04 ESM, Ubuntu 18.04 ESM and Ubuntu 20.04 ESM.
(CVE-2021-34549)

It was discovered that Tor did not properly manage memory under certain
circumstances. If a user were tricked into opening a specially crafted request,
a remote attacker could possibly use this issue to cause a crash, resulting in
a denial of service, or possibly reading sensitive data. This issue only
affected Ubuntu 18.04 ESM and Ubuntu 20.04 ESM. (CVE-2021-34550)

It was discovered that Tor mishandles the relationship between batch-signature
verification and single-signature verification. An attacker could possibly use
this issue to cause an assertion failure and then cause a denial of service.
This issue only affected Ubuntu 16.04 ESM, Ubuntu 18.04 ESM and Ubuntu 20.04
ESM. (CVE-2021-38385)

Update instructions

The problem can be corrected by updating your system to the following package versions:

Ubuntu 20.04

• tor - 0.4.2.7-1ubuntu0.1~esm1
  Available with Ubuntu Pro

Ubuntu 18.04

• tor - 0.3.2.10-1ubuntu0.2~esm2
  Available with Ubuntu Pro

Ubuntu 16.04

• tor - 0.2.9.14-1ubuntu1~16.04.3+esm1
  Available with Ubuntu Pro

Ubuntu 14.04

• tor - 0.2.4.27-1ubuntu0.1+esm2
  Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References

• CVE-2021-34550
• CVE-2019-8955
• CVE-2021-38385
• CVE-2021-34548
• CVE-2021-28089
• CVE-2021-28090
• CVE-2021-34549