9.1

CVSS Score

3.1

-

CVSS Score

Basic Information

CVE ID

CVE-2021-21693

GHSA ID

GHSA-929w-q433-4h9x

EPSS Score

0.77409%

CWE

CWE-285

Published

5/24/2022

Updated

12/7/2023

KEV Status

Technology

Java

Basic Information

CVE ID

GHSA ID

EPSS Score

CWE

Published

Updated

KEV Status

Technology

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CVE-2021-21693

CVE-2021-21693: Multiple vulnerabilities allow bypassing path filtering of agent-to-controller access control in Jenkins

The agent-to-controller security subsystem limits which files on the Jenkins controller can be accessed by agent processes.

Multiple vulnerabilities in the file path filtering implementation of Jenkins 2.318 and earlier, LTS 2.303.2 and earlier allow agent processes to read and write arbitrary files on the Jenkins controller file system, and obtain some information about Jenkins controller file systems.

SECURITY-2539 / CVE-2021-21693: When creating temporary files, permission to create files is only checked after they’ve been created.

We expect that most of these vulnerabilities have been present since SECURITY-144 was addressed in the 2014-10-30 security advisory.

Jenkins 2.319, LTS 2.303.3 addresses these security vulnerabilities.

SECURITY-2539 / CVE-2021-21693: When creating temporary files, permission to create files is checked before they are created based on an artificial path.

As some common operations are now newly subject to access control, it is expected that plugins sending commands from agents to the controller may start failing. Additionally, the newly introduced path canonicalization means that instances using a custom builds directory (Java system property jenkins.model.Jenkins.buildsDir) or partitioning JENKINS_HOME using symbolic links may fail access control checks. See the documentation for how to customize the configuration in case of problems.

If you are unable to immediately upgrade to Jenkins 2.319, LTS 2.303.3, you can install the Remoting Security Workaround Plugin. It will prevent all agent-to-controller file access using FilePath APIs. Because it is more restrictive than Jenkins 2.319, LTS 2.303.3, more plugins are incompatible with it. Make sure to read the plugin documentation before installing it.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2021-21693

CVE-2021-21693:

9.1

CVSS Score

3.1

-

CVSS Score

Basic Information

CVE ID

CVE-2021-21693

GHSA ID

GHSA-929w-q433-4h9x

EPSS Score

0.77409%

CWE

CWE-285

Published

5/24/2022

Updated

12/7/2023

KEV Status

Technology

Java

Basic Information

CVE ID

GHSA ID

EPSS Score

CWE

Published

Updated

KEV Status

Technology

Technical Details

CVSS Vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
org.jenkins-ci.main:jenkins-core	maven	>= 2.304, <= 2.318	2.319
org.jenkins-ci.main:jenkins-core	maven	< 2.303.3	2.303.3

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability (CVE-2021-21693) stems from improper authorization checks during temporary file/directory creation. The commit diff shows removal of deserialization guards (REJECT_LOCAL_CALLABLE_DESERIALIZATION and readResolve) for Mkdirs and Touch callables, which are executed when agents request file operations on the controller. Prior to the fix, these operations likely created files/directories first and then performed checks, violating the 'check-before-use' principle. The advisory explicitly cites SECURITY-2539, which addresses this flaw by enforcing pre-creation checks. The removed code suggests these callables were previously restricted but improperly validated during execution, leading to post-creation authorization bypasses.

Vulnerable functions

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WAF Protection Rules

WAF Rule

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Reasoning

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9.1

-

Basic Information

Basic Information

Concerned about an active attack path?

CVE-2021-21693: Multiple vulnerabilities allow bypassing path filtering of agent-to-controller access control in Jenkins

CVE-2021-21693:

9.1

-

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

9.1

9.1

Vulnerability IntelligenceMiggo AI

Root Cause Analysis

Vulnerable functions

WAF Protection Rules

WAF Rule

Reasoning

CVE-2021-21693: Multiple vulnerabilities allow bypassing path filtering of agent-to-controller access control in Jenkins

Basic Information

Basic Information

Vulnerability Intelligence
Miggo AI

Vulnerability Intelligence
Miggo AI

Vulnerability Intelligence
Miggo AI