CVE-2021-29475 : What You Need to Know

HedgeDoc (formerly known as CodiMD) is an open-source collaborative markdown editor. An attacker can receive arbitrary files from the file system via PDF export, impacting all instances with PDF export enabled. The vulnerability has a CVSS base score of 10, indicating a critical severity with high impact on confidentiality and integrity.

Understanding CVE-2021-29475

This CVE describes a code injection and SSRF vulnerability in HedgeDoc that allows attackers to read arbitrary files from the system through PDF export functionality.

What is CVE-2021-29475?

The vulnerability in HedgeDoc allows an attacker to retrieve arbitrary files from the file system by exporting a note to PDF, impacting instances with PDF export capabilities enabled.

The Impact of CVE-2021-29475

The exploit poses a critical risk, enabling attackers to access sensitive information such as the 'config.json' file and other data on the filesystem.

Technical Details of CVE-2021-29475

The vulnerability is a result of code injection in note content, exploiting PhantomJS rendering of 'file:///' references to exfiltrate data.

Vulnerability Description

Code injection allows malicious actors to read arbitrary files from the filesystem via PDF export, jeopardizing sensitive data.

Affected Systems and Versions

HedgeDoc versions prior to 1.5.0 are vulnerable to this exploit when PDF export is enabled.

Exploitation Mechanism

Attackers can exploit the vulnerability by modifying a note with the ability to export to PDF, accessing files through JavaScript rendering.

Mitigation and Prevention

To mitigate the CVE-2021-29475 vulnerability, update HedgeDoc to version 1.5.0 or disable PDF export functionality.

Immediate Steps to Take

Ensure HedgeDoc is updated to version 1.5.0 or higher and restrict PDF export capabilities if upgrading is not feasible.

Long-Term Security Practices

Regularly update HedgeDoc and other software components to prevent vulnerabilities and enhance system security.

Patching and Updates

Apply security patches promptly, follow best practices for secure configuration, and monitor for any security advisories from HedgeDoc.