CVE-2019-10160 in Python
Summary
by MITRE
A security regression of CVE-2019-9636 was discovered in python since commit d537ab0ff9767ef024f26246899728f0116b1ec3 affecting versions from v3.8.0a4 through v3.8.0b1, which still allows an attacker to exploit CVE-2019-9636 by abusing the user and password parts of a URL. When an application parses user-supplied URLs to store cookies, authentication credentials, or other kind of information, it is possible for an attacker to provide specially crafted URLs to make the application locate host-related information (e.g. cookies, authentication data) and send them to a different host than where it should, unlike if the URLs had been correctly parsed. The result of an attack may vary based on the application.
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Analysis
by VulDB Data Team • 09/28/2023
The vulnerability described in CVE-2019-10160 represents a critical security regression that undermines the proper handling of URL components in Python's standard library. This issue specifically affects Python versions from 3.8.0a4 through 3.8.0b1, where a previously identified vulnerability CVE-2019-9636 was supposed to be addressed but was inadvertently reintroduced due to a problematic code commit. The regression occurs within the URL parsing mechanisms that are fundamental to how Python applications process web resources, particularly when dealing with authentication credentials stored in URL format. The flaw resides in the improper handling of the user and password components of URLs, which creates a vector for attackers to manipulate host identification information during URL processing.
The technical implementation of this vulnerability stems from a flawed URL parsing algorithm that fails to correctly isolate host information from authentication credentials when processing URLs containing user and password components. When applications parse user-supplied URLs to extract cookies, authentication data, or other host-related information, the vulnerable code incorrectly interprets the host portion of the URL, allowing attackers to inject malicious host information through the authentication components. This creates a scenario where legitimate applications may store authentication tokens or cookies intended for one host but actually send them to a different host specified in the manipulated URL. The vulnerability operates at the protocol level where URL parsing logic fails to properly sanitize or validate the host component when user credentials are present in the URL structure, making it particularly dangerous for applications that rely on proper host identification for security purposes.
The operational impact of CVE-2019-10160 extends beyond simple data misplacement, potentially enabling sophisticated attacks such as cross-site request forgery, session hijacking, and credential theft. Applications that parse URLs for cookie storage, authentication handling, or resource access control become vulnerable to attackers who can craft URLs that redirect sensitive information to malicious hosts. This vulnerability particularly affects web applications, API clients, and any system that processes user-supplied URLs for authentication or session management purposes. The attack surface is broad since URL parsing is a fundamental operation in web applications, making this vulnerability potentially exploitable across numerous application types. The severity of the impact varies based on the specific application architecture and how it handles the parsed URL information, but the potential for unauthorized access or data leakage makes this a critical concern for system administrators and security professionals.
The vulnerability aligns with CWE-20 Improper Input Validation and CWE-345 Insufficient Verification of Data Authenticity, while mapping to ATT&CK techniques such as T1190 Exploit Public-Facing Application and T1566 Phishing with Social Engineering. The root cause of this issue demonstrates poor input sanitization practices in URL parsing components, where authentication credentials are not properly separated from host identification information. Security mitigations should include immediate patching of affected Python versions, implementing proper URL validation and sanitization routines, and deploying network monitoring to detect unusual host redirection patterns. Organizations should also consider implementing additional authentication layers and validating all URL components before processing, particularly when these URLs originate from untrusted sources. The vulnerability underscores the importance of thorough regression testing in security patches and demonstrates how seemingly minor code changes can reintroduce critical security flaws that affect widespread software ecosystems.