CVE-2020-2099

Description

Jenkins 2.213 and earlier, LTS 2.204.1 and earlier includes support for the Inbound TCP Agent Protocol/3 for communication between controller and agents. While [this protocol has been deprecated in 2018](https://www.jenkins.io/changelog-old/#v2.128) and was recently removed from Jenkins in 2.214, it could still easily be enabled in Jenkins LTS 2.204.1, 2.213, and older. This protocol incorrectly reuses encryption parameters which allow an unauthenticated remote attacker to determine the connection secret. This secret can then be used to connect attacker-controlled Jenkins agents to the Jenkins controller. Jenkins 2.204.2 no longer allows for the use of Inbound TCP Agent Protocol/3 by default. The system property `jenkins.slaves.JnlpSlaveAgentProtocol3.ALLOW_UNSAFE` can be set to `true` to allow enabling the Inbound TCP Agent Protocol/3 in Jenkins 2.204.2, but doing so is strongly discouraged. Inbound TCP Agent Protocol/3 was removed completely from Jenkins 2.214 and will not be part of Jenkins LTS after the end of the 2.204.x line.

How to fix CVE-2020-2099

To remediate CVE-2020-2099, upgrade the affected package to a fixed version below.

—upgrade to 2.218.1 or later
—upgrade to 2.204.2 or later

Is CVE-2020-2099 being exploited?

Low — EPSS is 0.6%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

from 0, < 2.218.1
from 0, < 2.204.2

CVSS scores

Source	Version	Severity	Vector
osv	CVSS 3.1	HIGH8.6	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:L