CVE-2014-8872 in FRITZ!Box
Summary
by MITRE
Improper Verification of Cryptographic Signature in AVM FRITZ!Box 6810 LTE after firmware 5.22, FRITZ!Box 6840 LTE after firmware 5.23, and other models with firmware 5.50.
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Analysis
by VulDB Data Team • 03/08/2022
The vulnerability CVE-2014-8872 represents a critical weakness in the cryptographic signature verification mechanism implemented within AVM FRITZBox 6810 LTE and FRITZ!Box 6840 LTE with respective firmware versions 5.22 and 5.23, along with other devices running firmware 5.50. This flaw resides in the router's firmware authentication system that is responsible for validating firmware updates and ensuring the integrity of software components. The improper verification process creates a pathway for attackers to bypass security controls designed to prevent unauthorized firmware modifications. The vulnerability is classified under CWE-322, which specifically addresses the weakness of key exchange without entity authentication, and also relates to CWE-347, concerning the lack of proper validation of cryptographic signatures. The attack surface extends beyond simple firmware manipulation to encompass potential system compromise through malicious code injection.
The technical implementation of this vulnerability stems from insufficient cryptographic signature validation routines within the router's update mechanism. When firmware updates are downloaded and installed, the system should verify that the digital signature matches the expected public key of the legitimate firmware publisher. However, the flawed implementation allows for signature verification to be bypassed or manipulated, enabling attackers to install modified firmware versions without proper authentication. This weakness particularly affects the router's secure boot process and firmware integrity checks that are fundamental to maintaining system security. The vulnerability aligns with ATT&CK technique T1068, which involves exploiting local system permissions to gain elevated privileges, and T1547, which focuses on establishing persistence through modification of system components. Attackers can exploit this vulnerability to install backdoors, modify network configurations, or gain persistent access to the network infrastructure.
The operational impact of CVE-2014-8872 is severe and multifaceted, affecting both network security and device integrity across enterprise and residential deployments. Organizations relying on AVM FRITZ!Box routers for network infrastructure face potential unauthorized access to their internal networks, as attackers can manipulate firmware to create persistent backdoors or redirect network traffic. The vulnerability undermines the trust model that routers rely on for secure updates, potentially allowing attackers to compromise the entire network perimeter. This weakness particularly threatens environments where these routers serve as primary network gateways, as they may become entry points for lateral movement within corporate networks or for launching attacks against external targets. The vulnerability also affects the router's ability to maintain secure communications with legitimate update servers, making it possible for attackers to perform man-in-the-middle attacks against firmware update processes. According to industry best practices and security frameworks, this vulnerability represents a critical risk to network security posture and requires immediate remediation.
Mitigation strategies for CVE-2014-8872 should prioritize immediate firmware updates from AVM, as the vendor has released patches addressing the cryptographic signature verification flaw. Network administrators must implement robust monitoring of router update processes and conduct regular security assessments of network infrastructure to detect potential exploitation attempts. The vulnerability requires a layered approach to security, including network segmentation to limit the impact of potential compromise, implementation of intrusion detection systems to monitor for unusual network behavior, and regular security audits of all network devices. Organizations should also consider disabling automatic firmware updates and manually verifying all firmware installations through trusted channels. Additionally, network administrators should implement network access controls and firewall rules to prevent unauthorized access to router management interfaces. The remediation process should include comprehensive network scanning to identify all affected devices, followed by coordinated firmware updates across all vulnerable systems. Security teams must also review and update incident response procedures to address potential exploitation of this vulnerability, ensuring that network defenders are prepared to respond to potential compromise scenarios that could arise from this cryptographic weakness.