CVE-2020-27488 in Miniserver
Summary
by MITRE • 01/14/2021
Loxone Miniserver devices with firmware before 11.1 (aka 11.1.9.3) are unable to use an authentication method that is based on the "signature of the update package." Therefore, these devices (or attackers who are spoofing these devices) can continue to use an unauthenticated cloud service for an indeterminate time period (possibly forever). Once an individual device's firmware is updated, and authentication occurs once, the cloud service recategorizes the device so that authentication is subsequently always required, and spoofing cannot occur.
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Analysis
by VulDB Data Team • 02/13/2021
The vulnerability identified as CVE-2020-27488 affects Loxone Miniserver devices running firmware versions prior to 11.1, specifically version 11.1.9.3 and earlier. This represents a critical security flaw in the device's authentication mechanism that undermines the integrity of the cloud service communication. The vulnerability stems from the device's inability to properly validate update package signatures, creating a persistent security gap that allows unauthorized access to cloud services. The flaw is particularly concerning because it affects the fundamental authentication process that should secure device-to-cloud communication, potentially enabling malicious actors to maintain unauthorized access indefinitely.
The technical implementation of this vulnerability lies in the authentication method that relies on signature verification of update packages. Devices running firmware versions before 11.1 lack the capability to properly validate these signatures, which creates a window of opportunity for attackers to spoof legitimate devices. This weakness allows unauthorized entities to continue using unauthenticated cloud services without proper device verification. The vulnerability essentially creates a backdoor that bypasses normal authentication procedures, enabling persistent unauthorized access to the cloud infrastructure that these devices utilize for various operational functions. This authentication bypass represents a direct violation of security principles and creates a persistent threat vector that remains active until firmware updates are deployed.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it fundamentally compromises the security posture of affected Loxone Miniserver deployments. Organizations relying on these devices for building automation and control systems face potential exposure of their entire network infrastructure to unauthorized access. The indeterminate timeframe of the vulnerability's persistence means that once an attacker gains access, they can maintain that access for potentially unlimited periods, creating a significant risk for critical infrastructure deployments. This vulnerability particularly affects industrial control systems and building automation environments where continuous operation and security are paramount. The cloud service component adds another layer of complexity, as compromised devices can potentially be used to attack other connected systems or exfiltrate sensitive data from the network.
The mitigation strategy for this vulnerability requires immediate deployment of firmware updates to version 11.1 or later, which implements proper signature validation mechanisms. Organizations should conduct comprehensive inventory assessments to identify all affected devices and prioritize their remediation based on risk exposure. Network segmentation and monitoring should be implemented to detect unauthorized cloud service access attempts, while also ensuring that proper access controls are in place for cloud service endpoints. Security teams should implement continuous monitoring of device communications to detect potential spoofing attempts or unauthorized access patterns. The vulnerability aligns with CWE-287 which addresses improper authentication issues, and the persistent nature of the flaw maps to ATT&CK technique T1078 which covers valid accounts and legitimate credentials for maintaining access. Organizations should also consider implementing additional security controls such as network access controls, device authentication mechanisms, and regular security assessments to prevent similar vulnerabilities from arising in the future.