CVE-2024-7592 in CPython
Summary
by MITRE • 08/19/2024
There is a LOW severity vulnerability affecting CPython, specifically the 'http.cookies' standard library module.
When parsing cookies that contained backslashes for quoted characters in the cookie value, the parser would use an algorithm with quadratic complexity, resulting in excess CPU resources being used while parsing the value.
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Analysis
by VulDB Data Team • 11/01/2025
The vulnerability identified as CVE-2024-7592 represents a performance degradation issue within the CPython standard library's http.cookies module. This flaw manifests when the cookie parser encounters cookie values containing backslashes within quoted characters, triggering an algorithm that exhibits quadratic time complexity behavior. The issue falls under the low severity classification according to standard vulnerability scoring systems, yet it presents significant operational concerns for applications that process high volumes of cookie data or those subject to denial of service attacks targeting parsing operations.
The technical root cause of this vulnerability lies in the implementation of the cookie parsing algorithm within the http.cookies module. When the parser encounters a cookie value that contains backslashes within quoted characters, it employs a parsing approach that scales quadratically with input size rather than maintaining linear or logarithmic complexity. This quadratic behavior occurs because the parser's internal logic processes each character in a manner that creates nested iterations, causing the computational overhead to grow exponentially as the length of the cookie value increases. The vulnerability specifically affects the handling of escaped characters within quoted cookie values, where backslashes are used to escape special characters in the cookie data.
From an operational perspective, this vulnerability creates potential for resource exhaustion attacks against applications that rely heavily on cookie processing. While the impact is classified as low severity, the quadratic complexity means that even moderately sized cookie values can cause significant CPU consumption during parsing operations. Attackers could potentially exploit this by crafting malicious cookie values with carefully constructed backslash sequences that would cause the parsing process to consume excessive computational resources. Applications that process large numbers of cookies or those that are exposed to untrusted cookie data sources would be particularly vulnerable to this type of resource exhaustion attack, potentially leading to degraded performance or complete service unavailability.
The vulnerability aligns with CWE-795 which addresses the issue of using regular expressions in a way that can cause quadratic behavior, and it also relates to ATT&CK technique T1496 which covers resource exhaustion attacks. Organizations should prioritize updating their CPython installations to versions that contain the patched http.cookies module implementation. The fix typically involves modifying the parsing algorithm to eliminate the quadratic complexity by implementing more efficient character processing techniques or by using optimized string manipulation methods. System administrators should also consider implementing rate limiting and input validation measures to prevent exploitation attempts while awaiting the official security patches. Monitoring for unusual CPU usage patterns during cookie processing operations can help detect potential exploitation attempts, and security teams should review their application's cookie handling logic to ensure proper input sanitization and validation practices are in place.