Summary
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 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.
Impact
Security-sensitive operations rely on values that are predictable or insufficiently random. Typical impact: forged tokens, guessable identifiers, or broken cryptographic protocols.
CVE-2020-2099 has a CVSS score of 8.6 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.204.2, 2.214); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
org.jenkins-ci.main:jenkins-core to 2.204.2 or later; org.jenkins-ci.main:jenkins-core to 2.214 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2020-2099? CVE-2020-2099 is a high-severity use of insufficiently random values vulnerability in org.jenkins-ci.main:jenkins-core (maven), affecting versions < 2.204.2. It is fixed in 2.204.2, 2.214. Security-sensitive operations rely on values that are predictable or insufficiently random.
- How severe is CVE-2020-2099? CVE-2020-2099 has a CVSS score of 8.6 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of org.jenkins-ci.main:jenkins-core are affected by CVE-2020-2099? org.jenkins-ci.main:jenkins-core (maven) versions < 2.204.2 is affected.
- Is there a fix for CVE-2020-2099? Yes. CVE-2020-2099 is fixed in 2.204.2, 2.214. Upgrade to this version or later.
- Is CVE-2020-2099 exploitable, and should I be worried? Whether CVE-2020-2099 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2020-2099 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2020-2099?
- Upgrade
org.jenkins-ci.main:jenkins-coreto 2.204.2 or later - Upgrade
org.jenkins-ci.main:jenkins-coreto 2.214 or later
- Upgrade