CVE-2023-36053 in Django
Summary
by MITRE • 07/03/2023
In Django 3.2 before 3.2.20, 4 before 4.1.10, and 4.2 before 4.2.3, EmailValidator and URLValidator are subject to a potential ReDoS (regular expression denial of service) attack via a very large number of domain name labels of emails and URLs.
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Analysis
by VulDB Data Team • 07/22/2023
The vulnerability identified as CVE-2023-36053 affects the Django web framework's validation mechanisms for email addresses and URLs, specifically targeting versions prior to 3.2.20, 4.1.10, and 4.2.3. This issue stems from the implementation of regular expressions within the EmailValidator and URLValidator classes, which are fundamental components used to validate user input in web applications. The vulnerability represents a classic ReDoS (Regular Expression Denial of Service) attack vector that exploits the exponential time complexity inherent in certain regular expression patterns when processing maliciously crafted input.
The technical flaw manifests when attackers provide email addresses or URLs containing an excessive number of domain name labels, typically in the form of multiple consecutive dots or nested subdomains. The regular expressions used by Django's validators are susceptible to catastrophic backtracking, where the validation process enters an exponential time complexity state that can consume system resources and cause significant delays or complete system unresponsiveness. This occurs because the regular expressions are not properly anchored or constrained, allowing the regex engine to explore an exponentially growing number of possible matches for malformed input.
The operational impact of this vulnerability is substantial for Django applications that rely on these validation mechanisms. An attacker could exploit this weakness by submitting maliciously crafted email addresses or URLs that trigger the ReDoS condition, potentially leading to service disruption, resource exhaustion, and denial of service for legitimate users. The vulnerability affects applications across multiple Django versions, making it a widespread concern that impacts a large portion of the Django ecosystem. Applications that do not properly sanitize user input or implement additional validation layers become particularly vulnerable to this attack vector.
Mitigation strategies for CVE-2023-36053 primarily involve upgrading to the patched versions of Django that address the regular expression patterns used in EmailValidator and URLValidator. Organizations should prioritize immediate patching of affected systems and conduct thorough testing to ensure compatibility with the updated validation logic. Additionally, implementing input rate limiting, request timeouts, and additional validation layers can provide defense-in-depth measures against potential exploitation attempts. The vulnerability aligns with CWE-400, which specifically addresses the improper handling of regular expressions, and can be categorized under ATT&CK technique T1499.004 for network denial of service attacks. Security teams should also consider implementing monitoring and alerting for unusual validation request patterns that might indicate exploitation attempts, as this vulnerability can be particularly effective in automated attack scenarios targeting web application frameworks.