CVE-2020-36320 in Vaadin
Summary
by MITRE • 04/24/2021
Unsafe validation RegEx in EmailValidator class in com.vaadin:vaadin-server versions 7.0.0 through 7.7.21 (Vaadin 7.0.0 through 7.7.21) allows attackers to cause uncontrolled resource consumption by submitting malicious email addresses.
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Analysis
by VulDB Data Team • 04/29/2021
The vulnerability identified as CVE-2020-36320 resides within the EmailValidator class of the vaadin-server component in Vaadin versions 7.0.0 through 7.7.21. This issue represents a classic example of insecure regular expression usage that can be exploited to cause denial of service through resource exhaustion. The vulnerability stems from the implementation of an unsafe validation regular expression that fails to properly handle malicious input patterns designed to trigger catastrophic backtracking behavior.
The technical flaw manifests in the EmailValidator's regular expression pattern which does not adequately account for the complexity and potential recursion that malicious email addresses can introduce during pattern matching operations. When an attacker submits a specially crafted email address containing repeated patterns or nested structures, the regular expression engine enters into a state of exponential backtracking where it repeatedly attempts different matching combinations. This behavior is classified under CWE-1333 which specifically addresses insecure regular expression patterns that can lead to resource exhaustion attacks. The vulnerability allows attackers to consume excessive CPU cycles and memory resources during the validation process, effectively creating a denial of service condition that can impact the availability of the application.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the overall system stability and availability. In high-traffic applications where email validation occurs frequently, attackers can leverage this vulnerability to exhaust system resources and prevent legitimate users from submitting email addresses. This type of resource exhaustion attack aligns with ATT&CK technique T1499.004 which covers network denial of service attacks and can be particularly devastating in production environments where service availability is critical. The vulnerability affects the entire Vaadin 7.x series, making it a widespread concern for organizations that have not migrated to newer versions of the framework.
Organizations should prioritize immediate mitigation through version upgrades to Vaadin 8.0.0 or later, which contain fixed implementations of the email validation logic. The recommended remediation strategy involves applying the latest security patches and upgrading to supported versions of the Vaadin framework to eliminate the vulnerable regular expression patterns. Additionally, implementing input validation controls and rate limiting mechanisms can provide additional defense in depth. Security teams should also monitor for exploitation attempts and consider implementing network-based detection rules that can identify suspicious email validation patterns. The vulnerability demonstrates the critical importance of proper regular expression design and validation in security-critical components, particularly in web application frameworks where input validation occurs frequently and at scale.