CVE-2019-5134 in PFC100
Summary
by MITRE
An exploitable regular expression without anchors vulnerability exists in the Web-Based Management (WBM) authentication functionality of WAGO PFC200 versions 03.00.39(12) and 03.01.07(13), and WAGO PFC100 version 03.00.39(12). A specially crafted authentication request can bypass regular expression filters, resulting in sensitive information disclosure.
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Analysis
by VulDB Data Team • 04/13/2024
The vulnerability identified as CVE-2019-5134 represents a critical security flaw in the web-based management interface of WAGO industrial automation products including PFC200 and PFC100 series devices. This issue manifests within the authentication subsystem where improperly configured regular expression patterns fail to properly validate user input, creating a pathway for unauthorized access and information disclosure. The vulnerability affects specific firmware versions of these industrial control devices, making it particularly concerning for operational technology environments where security is paramount.
The technical root cause of this vulnerability stems from the absence of proper anchors in regular expression patterns used for validating authentication credentials within the web management interface. When developers create regular expressions for input validation, they must ensure that these patterns match the entire input string rather than partial matches. Without anchors such as ^ and $, the regular expression engine may find a match anywhere within the input string, allowing attackers to bypass validation by appending malicious content to legitimate credentials. This pattern matching flaw falls under the CWE-185 category of "Incorrect Regular Expression" and represents a common vulnerability in security implementations where input validation is insufficiently constrained.
The operational impact of this vulnerability extends beyond simple authentication bypass to potentially expose sensitive operational data and system configurations. Industrial control systems like those manufactured by WAGO are critical infrastructure components where unauthorized access can lead to significant operational disruptions, safety hazards, or even physical damage to equipment. Attackers exploiting this vulnerability could gain unauthorized access to system management interfaces, potentially leading to configuration changes, data exfiltration, or the deployment of malicious payloads within industrial networks. The implications are particularly severe in environments where these devices control critical manufacturing processes or safety systems.
Mitigation strategies for CVE-2019-5134 should prioritize immediate firmware updates from WAGO to address the vulnerable regular expression implementations. Organizations must also implement network segmentation to limit access to these management interfaces, requiring strong authentication mechanisms including multi-factor authentication where possible. Security monitoring should be enhanced to detect unusual authentication patterns or attempts to access management interfaces from unauthorized sources. The vulnerability aligns with ATT&CK technique T1078 for Valid Accounts and T1566 for Phishing, as attackers may leverage this weakness to establish persistent access to industrial control systems. Additionally, implementing proper input validation frameworks and conducting regular security assessments of industrial control system interfaces can prevent similar vulnerabilities from emerging in future deployments.