CVE-2021-31409 in Vaadin
Summary
by MITRE • 05/06/2021
Unsafe validation RegEx in EmailValidator component in com.vaadin:vaadin-compatibility-server versions 8.0.0 through 8.12.4 (Vaadin versions 8.0.0 through 8.12.4) allows attackers to cause uncontrolled resource consumption by submitting malicious email addresses.
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Analysis
by VulDB Data Team • 05/09/2021
The vulnerability CVE-2021-31409 affects the EmailValidator component within the vaadin-compatibility-server library version 8.0.0 through 8.12.4, representing a critical security flaw that enables attackers to perform resource exhaustion attacks. This issue stems from the implementation of an unsafe regular expression pattern that fails to properly validate email addresses, creating a potential denial of service vector that can be exploited by malicious actors. The vulnerability specifically targets the input validation mechanism used by Vaadin applications, which are widely deployed in enterprise environments for building web user interfaces. The unsafe validation approach allows attackers to craft email addresses that trigger catastrophic backtracking in the regular expression engine, causing excessive CPU and memory consumption during validation processing.
The technical flaw manifests through the use of a poorly constructed regular expression that does not account for the exponential time complexity inherent in certain regex patterns when processing malicious input. This vulnerability aligns with CWE-1333, which categorizes issues related to regular expression vulnerabilities, particularly those involving catastrophic backtracking scenarios. The flaw enables attackers to submit email addresses containing specific patterns that cause the regex engine to perform an exponential number of operations, leading to uncontrolled resource consumption and potential system instability. When the EmailValidator processes these malicious inputs, the system experiences significant performance degradation or complete service unavailability.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can affect entire application availability and user experience within Vaadin-based systems. Organizations utilizing affected versions of the vaadin-compatibility-server library may experience cascading failures where legitimate users cannot access email validation features, and the system becomes vulnerable to resource exhaustion attacks that can impact other application components. The vulnerability affects applications built on Vaadin framework versions 8.0.0 through 8.12.4, which were widely adopted in enterprise environments, making the potential attack surface substantial. Security researchers have identified that the vulnerability can be exploited through various attack vectors including web forms, API endpoints, and any application interface that relies on email validation functionality.
Mitigation strategies for CVE-2021-31409 should prioritize immediate patching of affected vaadin-compatibility-server versions to the latest available releases that contain fixed regular expression implementations. Organizations should implement input validation layers at multiple points within their applications to reduce the impact of potential exploitation attempts, including rate limiting and additional validation mechanisms beyond the vulnerable component. The ATT&CK framework categorizes this vulnerability under T1499.004, which deals with network denial of service, and T1210, which addresses exploitation of remote services through input validation weaknesses. Additionally, security teams should conduct comprehensive vulnerability assessments to identify all applications using affected Vaadin versions and implement monitoring solutions to detect unusual resource consumption patterns that may indicate exploitation attempts. Organizations should also consider implementing web application firewalls and input sanitization measures to provide additional protection layers against similar vulnerabilities in other components of their web applications.