CVE-2016-9014 in Django
Summary
by MITRE
Django before 1.8.x before 1.8.16, 1.9.x before 1.9.11, and 1.10.x before 1.10.3, when settings.DEBUG is True, allow remote attackers to conduct DNS rebinding attacks by leveraging failure to validate the HTTP Host header against settings.ALLOWED_HOSTS.
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Analysis
by VulDB Data Team • 05/24/2019
This vulnerability affects Django web applications running versions prior to 1.8.16, 1.9.11, and 1.10.3 when the DEBUG setting is enabled. The flaw stems from insufficient validation of the HTTP Host header against the ALLOWED_HOSTS configuration parameter, creating a significant security risk that can be exploited by remote attackers. When settings.DEBUG is set to True, Django becomes more permissive in handling incoming requests, but this permissiveness extends to host header validation which should normally act as a crucial security boundary. The vulnerability allows attackers to perform DNS rebinding attacks by manipulating the Host header in HTTP requests, effectively bypassing the intended host validation mechanisms. This occurs because the application fails to properly validate that the requested host domain matches the configured ALLOWED_HOSTS list, enabling attackers to redirect traffic to arbitrary hosts. The technical implementation of this vulnerability aligns with CWE-284 Access Control Issues, specifically related to improper access control mechanisms that fail to validate user inputs against security policies. From an operational perspective, this vulnerability represents a critical risk as it can be exploited without authentication and can potentially lead to unauthorized access to internal systems, data exfiltration, or further exploitation within the network environment. The attack vector is particularly dangerous because it leverages the common practice of enabling DEBUG mode in development environments while inadvertently exposing production systems to remote attackers. Attackers can utilize this vulnerability to perform reconnaissance, access internal services that should normally be protected by host-based access controls, and potentially escalate privileges within the application environment.
The impact of this vulnerability extends beyond simple information disclosure as it can enable more sophisticated attacks within the context of the ATT&CK framework. Specifically, this weakness can be categorized under T1212 Exploitation for Credential Access and T1071.004 Application Layer Protocol DNS, where attackers can leverage the DNS rebinding technique to bypass network security controls. The vulnerability is particularly concerning in environments where Django applications are deployed with DEBUG mode enabled in production or staging environments, as this configuration is common in development workflows but creates dangerous security exposures. When combined with other network-level vulnerabilities or misconfigurations, this flaw can facilitate lateral movement within an organization's network infrastructure, as attackers can use the compromised application to probe internal services that would normally be protected by proper host validation. The security implications are exacerbated by the fact that many organizations maintain DEBUG mode enabled during testing phases but fail to disable it in production environments, creating a persistent attack surface that can be exploited by threat actors.
Mitigation strategies for this vulnerability require immediate attention and systematic implementation across affected Django installations. The primary and most effective mitigation is to ensure that settings.DEBUG is set to False in production environments, as this prevents the vulnerability from being exploitable. Additionally, administrators must properly configure the ALLOWED_HOSTS setting to include only trusted domains and subdomains that should be permitted to access the application. This configuration should be comprehensive and validated against the actual deployment environment to prevent any accidental inclusion of wildcard entries that could undermine security controls. Organizations should also implement network-level controls such as firewalls and intrusion detection systems to monitor for suspicious Host header values and potential DNS rebinding attempts. Regular security audits and code reviews should be conducted to ensure that DEBUG mode is not enabled in production environments, and automated deployment pipelines should include checks to verify that security configurations are properly set before application deployment. The remediation process should also include updating to patched versions of Django, specifically versions 1.8.16, 1.9.11, and 1.10.3 or later, which contain the necessary fixes for this vulnerability. Security teams should implement monitoring for unusual patterns in Host header values and establish incident response procedures to quickly address any potential exploitation attempts. This vulnerability demonstrates the critical importance of proper configuration management and the dangers of leaving development security features enabled in production environments, highlighting the need for comprehensive security awareness training and robust deployment security practices.