CVE-2018-19789 : Exploit Details and Defense Strategies

A vulnerability has been identified in Symfony versions 2.7.x before 2.7.50, 2.8.x before 2.8.49, 3.x before 3.4.20, 4.0.x before 4.0.15, 4.1.x before 4.1.9, and 4.2.x before 4.2.1 that could lead to remote code execution.

Understanding CVE-2018-19789

This CVE involves a security issue in Symfony versions that could potentially allow an attacker to execute remote code.

What is CVE-2018-19789?

This vulnerability arises when using the scalar type hint

string

in a setter method of a class designated as the

data_class

of a form. If a file upload is submitted to the corresponding field instead of a regular text input, it may disclose the path of the uploaded file, potentially leading to remote code execution.

The Impact of CVE-2018-19789

The vulnerability could be exploited to execute remote code, especially when combined with a local file inclusion issue.

Technical Details of CVE-2018-19789

This section provides more technical insights into the vulnerability.

Vulnerability Description

When using the

string

scalar type hint in a setter method of a class designated as the

data_class

of a form, uploading a file to the field may trigger the disclosure of the file path, potentially enabling remote code execution.

Affected Systems and Versions

Symfony versions 2.7.x before 2.7.50
Symfony versions 2.8.x before 2.8.49
Symfony versions 3.x before 3.4.20
Symfony versions 4.0.x before 4.0.15
Symfony versions 4.1.x before 4.1.9
Symfony versions 4.2.x before 4.2.1

Exploitation Mechanism

The vulnerability occurs when a file upload is submitted to a field instead of a regular text input, triggering the

UploadedFile::__toString()

function and potentially disclosing the path of the uploaded file, which could be exploited for remote code execution.

Mitigation and Prevention

Protecting systems from CVE-2018-19789 requires immediate actions and long-term security practices.

Immediate Steps to Take

Update Symfony to the patched versions (2.7.50, 2.8.49, 3.4.20, 4.0.15, 4.1.9, 4.2.1) to mitigate the vulnerability.
Review and restrict file upload capabilities to trusted sources.

Long-Term Security Practices

Regularly monitor and apply security updates for Symfony and related components.
Implement secure coding practices to prevent similar vulnerabilities in the future.

Patching and Updates

Ensure timely patching and updates for Symfony to address security vulnerabilities.