CVE-2021-29488 : Security Advisory and Response

SABnzbd, an open-source binary newsreader, was found to have a vulnerability that could be exploited by malicious PAR2 files to create files outside the configured Download Folder. This CVE, with a base score of 4.3, poses a medium risk and affects versions of SABnzbd prior to 3.2.1.

Understanding CVE-2021-29488

This section provides insights into the nature of the vulnerability and its implications.

What is CVE-2021-29488?

CVE-2021-29488 involves a vulnerability in SABnzbd that allows the

filesystem.renamer()

function to write downloaded files outside the intended directory via crafted PAR2 files.

The Impact of CVE-2021-29488

The vulnerability could potentially allow threat actors to manipulate PAR2 files, leading to files being created beyond the designated Download Folder, causing integrity concerns.

Technical Details of CVE-2021-29488

This section delves into the specifics of the vulnerability, affected systems, and possible exploitation methods.

Vulnerability Description

The flaw in SABnzbd's

filesystem.renamer()

function enables files to be written outside the Download Folder, opening avenues for unauthorized file creation.

Affected Systems and Versions

SABnzbd versions prior to 3.0.0 for Windows and versions before 3.2.1 for other operating systems are susceptible to this vulnerability.

Exploitation Mechanism

Threat actors can exploit this vulnerability by crafting malicious PAR2 files to deceive the function into writing files to unauthorized locations.

Mitigation and Prevention

This section outlines steps to mitigate the risks associated with CVE-2021-29488 and protect systems from potential exploitation.

Immediate Steps to Take

To address the issue, users are advised to limit downloads to NZBs without PAR2 files, restrict write permissions for SABnzbd, or update to version 3.2.1 or later.

Long-Term Security Practices

Implementing file system monitoring, applying the principle of least privilege, and regularly updating SABnzbd are crucial for long-term security.

Patching and Updates

Users should promptly apply patches and updates released by SABnzbd to address the vulnerability and enhance system security.