CVE-2023-23969 in Django
Summary
by MITRE • 02/01/2023
In Django 3.2 before 3.2.17, 4.0 before 4.0.9, and 4.1 before 4.1.6, the parsed values of Accept-Language headers are cached in order to avoid repetitive parsing. This leads to a potential denial-of-service vector via excessive memory usage if the raw value of Accept-Language headers is very large.
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Analysis
by VulDB Data Team • 07/01/2025
The vulnerability described in CVE-2023-23969 represents a significant denial-of-service weakness within the Django web framework that affects multiple versions including 3.2.x prior to 3.2.17, 4.0.x prior to 4.0.9, and 4.1.x prior to 4.1.6. This issue stems from Django's caching mechanism for parsed Accept-Language header values, which is designed to optimize performance by avoiding redundant parsing operations. However, the implementation contains a critical flaw that allows malicious actors to exploit the caching behavior for resource exhaustion attacks. The vulnerability specifically targets the HTTP Accept-Language header processing where Django caches parsed values to improve efficiency, but this caching becomes problematic when handling exceptionally large raw header values.
The technical flaw manifests in how Django handles HTTP Accept-Language headers by maintaining a cache of parsed values to avoid repeated parsing of identical or similar headers. When an attacker sends a malformed or excessively large Accept-Language header, the system processes and caches this parsed representation. The vulnerability becomes apparent when multiple large headers are processed, leading to excessive memory consumption as each parsed value remains cached indefinitely. This caching mechanism lacks proper size limitations or eviction policies, allowing an attacker to gradually consume system memory resources through repeated requests with large header values. The issue is classified under CWE-400 as an excessive resource consumption vulnerability, specifically manifesting as a denial-of-service condition through memory exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise entire application availability and system stability. Attackers can systematically consume memory resources by sending requests with progressively larger Accept-Language headers, leading to application slowdowns, crashes, or complete unavailability. This vulnerability affects web applications built on Django framework where the application processes HTTP requests with Accept-Language headers, making it particularly dangerous for high-traffic sites or applications that rely heavily on internationalization features. The memory exhaustion can cascade into system-level issues, affecting not only the vulnerable Django application but potentially other services running on the same infrastructure. Organizations using Django frameworks without the patched versions face significant risk of service degradation or complete outages.
Mitigation strategies for this vulnerability involve implementing immediate patches to upgrade to the affected versions that contain the fix, specifically Django 3.2.17, 4.0.9, and 4.1.6. Security teams should also consider implementing rate limiting and header size restrictions at reverse proxies or load balancers to prevent large header values from reaching the Django application. Additionally, monitoring for unusual memory consumption patterns and implementing proper cache eviction policies can help detect and prevent exploitation attempts. Organizations should also review their application's header processing logic and consider implementing additional validation layers to sanitize Accept-Language header values before they reach the caching mechanism. The ATT&CK framework categorizes this vulnerability under T1499.004 as an application denial-of-service attack, emphasizing the importance of proper resource management and input validation in preventing such exploitation vectors.