CVE-2024-11168 is a vulnerability in the Python Software Foundation's CPython implementation, specifically in the urllib.parse module's urlsplit() and urlparse() functions. These functions are responsible for parsing URLs and validating host components. The vulnerability arises because these functions improperly validate bracketed hosts enclosed in square brackets ([]), which are intended to represent IPv6 or IPvFuture addresses according to RFC 3986. However, the affected functions allow hosts within brackets that are not valid IPv6 or IPvFuture addresses. This improper validation can cause inconsistencies when a URL is processed by multiple parsers or components that enforce stricter RFC compliance. An attacker can exploit this discrepancy to craft malicious URLs that bypass security checks, leading to Server-Side Request Forgery (SSRF) attacks. SSRF allows an attacker to induce the server to make HTTP requests to arbitrary internal or external resources, potentially exposing sensitive internal services or data. The vulnerability affects CPython versions 0 (likely meaning all versions prior to 3.10), 3.10.0, 3.11.0, and the early 3.12.0a1 alpha release. The CVSS 4.0 base score is 6.3, indicating medium severity, with network attack vector, high attack complexity, no privileges required, no user interaction, and limited impact on integrity. No known exploits have been reported in the wild at the time of publication. The vulnerability is classified under CWE-918 (Server-Side Request Forgery).

For European organizations, this vulnerability poses a risk primarily to web applications and services developed in Python that rely on urllib.parse for URL processing. SSRF vulnerabilities can be leveraged to access internal network resources that are otherwise inaccessible from the internet, potentially leading to data exposure, unauthorized access to internal APIs, or pivoting within the network. Organizations in sectors such as finance, healthcare, government, and critical infrastructure, which often use Python for backend services, could be targeted to gain access to sensitive internal systems. The impact is heightened in environments where multiple URL parsers or security controls rely on different URL validation logic, allowing attackers to bypass protections. Additionally, cloud service providers and SaaS companies operating in Europe that use vulnerable Python versions may face risks of internal resource exposure. The medium severity rating reflects that exploitation requires some complexity and careful crafting of URLs, but no authentication or user interaction is needed, increasing the attack surface. The absence of known exploits suggests a window for proactive mitigation.

1. Upgrade CPython to a patched version once released by the Python Software Foundation that corrects the bracketed host validation logic in urllib.parse. 2. In the interim, implement strict input validation on URLs before processing, ensuring that bracketed hosts conform strictly to valid IPv6 or IPvFuture formats. 3. Employ network-level controls such as egress filtering and internal firewall rules to restrict server-initiated HTTP requests to trusted destinations only, limiting SSRF impact. 4. Use application-layer protections like web application firewalls (WAFs) configured to detect and block suspicious URL patterns or SSRF attempts. 5. Review and audit codebases for multiple URL parsing steps or components that may interpret URLs differently, standardizing on a single, secure parsing method. 6. Monitor logs for unusual outbound requests or anomalies in URL processing that could indicate exploitation attempts. 7. Educate developers about the risks of SSRF and the importance of proper URL validation and sanitization.