CVE-2021-29449 in Pi-hole
Summary
by MITRE • 04/15/2021
Pi-hole is a Linux network-level advertisement and Internet tracker blocking application. Multiple privilege escalation vulnerabilities were discovered in version 5.2.4 of Pi-hole core. See the referenced GitHub security advisory for details.
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Analysis
by VulDB Data Team • 04/06/2026
The vulnerability identified as CVE-2021-29449 represents a critical privilege escalation flaw within Pi-hole version 5.2.4, a widely deployed network-level advertisement and Internet tracker blocking solution. This issue affects the core functionality of the Pi-hole system, which operates as a DNS-based content blocker that can be deployed on Linux systems to filter unwanted advertisements and track cookies across network traffic. The vulnerability stems from improper access controls and privilege management within the application's core components, specifically impacting the administrative interface and system-level operations that require elevated permissions. Pi-hole's architecture typically runs as a daemon process with specific user privileges, but the flaw allows unauthorized users to escalate their privileges and gain administrative access to the underlying system.
The technical implementation of this privilege escalation vulnerability involves a combination of insufficient input validation and improper privilege handling within the application's authentication and authorization mechanisms. Attackers can exploit this weakness by crafting specific requests or manipulating system calls that bypass normal access controls, potentially allowing them to execute arbitrary commands with root privileges. The vulnerability's impact is particularly severe because Pi-hole systems often run with elevated privileges to manage network traffic and modify system configurations, making the privilege escalation path directly relevant to system compromise. This type of vulnerability falls under CWE-276, which addresses improper privilege management, and aligns with ATT&CK technique T1068, which covers local privilege escalation through system binary manipulation.
The operational impact of CVE-2021-29449 extends beyond simple access control violations, as it can lead to complete system compromise and persistent backdoor access for attackers. Once exploited, the vulnerability allows adversaries to modify the Pi-hole configuration files, install malicious software, or redirect network traffic to malicious endpoints, effectively compromising the entire network's security posture. Organizations relying on Pi-hole for network filtering and security enforcement face significant risk, as the vulnerability could enable attackers to bypass the very security measures the system was designed to provide. Network administrators who depend on Pi-hole for traffic monitoring and filtering may find their systems compromised without detection, potentially allowing for extended periods of unauthorized access and data exfiltration.
Mitigation strategies for this vulnerability require immediate patching of affected Pi-hole installations to version 5.3.0 or later, which contains the necessary security fixes and access control improvements. System administrators should also implement additional monitoring measures to detect unusual activity patterns that might indicate exploitation attempts, particularly focusing on authentication failures and privilege escalation events. Network segmentation and firewall rules should be reviewed to limit access to Pi-hole administrative interfaces, while multi-factor authentication should be implemented where possible. Regular security audits of network infrastructure and proper privilege management practices should be enforced to prevent similar vulnerabilities from arising in other system components. The fix addresses the underlying privilege escalation mechanism by implementing proper access controls and validating user permissions before executing privileged operations, aligning with industry best practices for secure application development and system hardening.