CVE-2015-2689 Denial of service in Tor

High 7.5 Published 24 Jan 2020 Updated 6 Aug 2024

Remote attackers can cause a denial of service in Tor by sending crafted packets during high DNS load, leading to daemon exit.

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

What is CVE-2015-2689?

CVE-2015-2689 is a high-severity denial of service vulnerability in The Tor Project Tor, published on 24 Jan 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Tor before 0.2.4.26 and 0.2.5.x before 0.2.5.11 does not properly handle pending-connection resolve states during periods of high DNS load, which allows remote attackers to cause a denial of service (assertion failure and daemon exit) via crafted packets.

Weakness: CWE-20

Which versions are affected by CVE-2015-2689?

It affects 1 product.

Products include Torproject Tor.

How do I fix CVE-2015-2689?

Upgrade to a fixed version.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2015-2689 being exploited?

There is no known exploitation of CVE-2015-2689 in the wild and no public exploit code.

Sources

Also known as DEBIAN-CVE-2015-2689, GHSA-7r2c-ch3m-w27x, UBUNTU-CVE-2015-2689.