CVE-2020-28501 in es6-crawler-detect
Summary
by MITRE • 03/22/2021
This affects the package es6-crawler-detect before 3.1.3. No limitation of user agent string length supplied to regex operators.
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Analysis
by VulDB Data Team • 04/03/2021
The vulnerability identified as CVE-2020-28501 resides within the es6-crawler-detect package, a JavaScript library designed to identify web crawlers and bots by analyzing user agent strings. This particular flaw affects versions prior to 3.1.3 and represents a critical security oversight that could enable malicious actors to exploit the package's handling of user agent data. The issue stems from the library's failure to impose any limits on the length of user agent strings that are processed through regular expression operations, creating a potential vector for denial of service and resource exhaustion attacks.
The technical flaw manifests in the package's inadequate input validation and sanitization mechanisms. When the es6-crawler-detect library processes user agent strings, it directly feeds these inputs into regular expression engines without implementing any length restrictions or bounds checking. This behavior creates a classic regular expression denial of service vulnerability, where an attacker can craft an exceptionally long user agent string that causes the regular expression engine to consume excessive computational resources or even crash. The vulnerability falls under the CWE-770 category of allocation of resources without limits or throttling, specifically affecting the processing of user agent strings through regex operations.
The operational impact of this vulnerability extends beyond simple denial of service scenarios. Attackers could potentially exploit this weakness to consume server resources, causing legitimate requests to fail or slowing down the entire application. In web applications that rely on crawler detection for access control, content filtering, or analytics purposes, this vulnerability could enable bypass of security measures or disruption of legitimate functionality. The attack surface is particularly concerning in environments where the package is used in server-side applications or APIs that process user agent strings from untrusted sources, as these scenarios provide direct paths for exploitation.
Mitigation strategies for CVE-2020-28501 should focus on upgrading to version 3.1.3 or later of the es6-crawler-detect package, which includes proper input length validation and resource limiting mechanisms. Additionally, administrators should implement application-level rate limiting and input sanitization measures to prevent malicious user agent strings from reaching the vulnerable code paths. The remediation process should include thorough code review to identify any other instances where similar regex processing occurs without proper input validation, as this pattern may exist elsewhere in the application stack. Security teams should also consider implementing monitoring and alerting for unusual resource consumption patterns that might indicate exploitation attempts targeting this vulnerability. This remediation aligns with ATT&CK technique T1499.004 for resource exhaustion and emphasizes the importance of proper input validation as outlined in the OWASP Top Ten categories related to injection flaws and resource management.