8.6

CVSS Score

3.0

-

CVSS Score

Basic Information

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CVE-2020-2099

CVE-2020-2099: Inbound TCP Agent Protocol/3 authentication bypass in Jenkins

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.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2020-2099

CVE-2020-2099:

8.6

CVSS Score

3.0

-

CVSS Score

Basic Information

Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
org.jenkins-ci.main:jenkins-core	maven	< 2.204.2	2.204.2
org.jenkins-ci.main:jenkins-core	maven	>= 2.205, < 2.214	2.214

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability stems from the Inbound TCP Agent Protocol/3 implementation in JnlpSlaveAgentProtocol3. The commit diff shows this protocol was disabled by default via an ExtensionFilter, indicating its active presence was the vulnerability source. The handle() method processes connections using this protocol, while createHandler() initializes the flawed cryptographic handler. These functions directly implement the insecure protocol mechanics described in CWE-323/CWE-330.

Vulnerable functions

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WAF Protection Rules

WAF Rule

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Reasoning

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8.6

-

Basic Information

Basic Information

Concerned about an active attack path?

CVE-2020-2099: Inbound TCP Agent Protocol/3 authentication bypass in Jenkins

CVE-2020-2099:

8.6

-

Basic Information

Basic Information

Technical Details

Technical Details

Vulnerability IntelligenceMiggo AI

Root Cause Analysis

Vulnerable functions

WAF Protection Rules

WAF Rule

Reasoning

Vulnerability IntelligenceMiggo AI

Technical Details

8.6

8.6

CVE-2020-2099: Inbound TCP Agent Protocol/3 authentication bypass in Jenkins

Basic Information

Basic Information

Vulnerability IntelligenceMiggo AI

Root Cause Analysis

Vulnerable functions

WAF Protection Rules

WAF Rule

Reasoning

Vulnerability Intelligence
Miggo AI

Vulnerability Intelligence
Miggo AI

Vulnerability Intelligence
Miggo AI