CVE-2018-0491 Use after free in Tor

High 7.5 Published 5 Mar 2018 Updated 5 Aug 2024

Remote attackers can crash Tor relays via a use-after-free flaw in the KIST implementation, requiring an upgrade to mitigate.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2018-0491?

CVE-2018-0491 is a high-severity use after free vulnerability in Tor, published on 5 Mar 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

A use-after-free issue was discovered in Tor 0.3.2.x before 0.3.2.10. It allows remote attackers to cause a denial of service (relay crash) because the KIST implementation allows a channel to be added more than once in the pending list.

Weakness: CWE-416

Which versions are affected by CVE-2018-0491?

It affects 1 product.

Products include Torproject Tor.

How do I fix CVE-2018-0491?

Upgrade to a fixed version.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2018-0491 being exploited?

There is no known exploitation of CVE-2018-0491 in the wild and no public exploit code.

Public exploit code: 1 Exploit-DB entry.

Sources

Also known as DEBIAN-CVE-2018-0491, GHSA-8wr4-7fjq-4qxw, UBUNTU-CVE-2018-0491.