CVE-2024-23644 is a vulnerability in the trillium-rs Rust toolkit, specifically in the trillium-http and trillium-client libraries prior to versions 0.3.12 and 0.5.4 respectively. The issue arises from improper validation of HTTP header names and values, allowing injection of CRLF (Carriage Return Line Feed) sequences. This improper neutralization of CRLF sequences (CWE-113) can lead to HTTP request/response splitting attacks. When an attacker can control header values or names and insert CRLF sequences, they can manipulate the HTTP protocol flow, causing the client and server to become desynchronized. This can enable various malicious activities such as request smuggling, response splitting, cross-site scripting (XSS), cache poisoning, and server-side request forgery (SSRF). The vulnerability affects scenarios where untrusted input is inserted into headers without proper sanitization. The flaw exists because trillium-http's HeaderName and HeaderValue types were constructed without checking for illegal bytes, allowing CRLF injection. In the fixed versions, invalid headers or values are omitted or cause errors before network transmission, preventing exploitation. The vulnerability has a CVSS 3.1 score of 6.8 (medium severity) with attack vector network, requiring low privileges but no user interaction, and impacts confidentiality and integrity but not availability. No known exploits are reported in the wild yet. The root cause is insufficient input validation and sanitization of HTTP headers in the affected trillium-rs versions, which is critical since HTTP headers are a fundamental part of web communication and security.

For European organizations using trillium-rs in their web applications or services, this vulnerability could lead to significant security risks. Exploitation could allow attackers to intercept or manipulate HTTP traffic, leading to data leakage, session hijacking, or unauthorized access to internal resources through SSRF. Confidentiality and integrity of communications could be compromised, especially in environments where trillium-rs is used to build APIs, microservices, or web servers. Given trillium-rs is a Rust-based toolkit, it may be popular among organizations adopting Rust for secure and performant web services. The impact is heightened in sectors handling sensitive data such as finance, healthcare, and government services prevalent in Europe. Additionally, the ability to pivot attacks via request/response splitting could facilitate lateral movement within networks, increasing the risk of broader compromise. Although no exploits are currently known, the medium severity rating and network attack vector suggest that attackers with some level of access or control over input headers could exploit this vulnerability remotely. This necessitates prompt attention to prevent potential data breaches or service disruptions.

European organizations should immediately upgrade trillium-http to version 0.3.12 or later and trillium-client to version 0.5.4 or later to benefit from the built-in validation and sanitization fixes. Until upgrades are applied, developers must implement strict input validation and sanitization on all untrusted data incorporated into HTTP headers, explicitly disallowing carriage return (\r), newline (\n), and null characters. Security teams should audit codebases for any direct or indirect usage of trillium-http and trillium-client libraries and review how header values and names are constructed and sourced. Employing Web Application Firewalls (WAFs) with rules to detect and block CRLF injection attempts can provide additional protection. Monitoring HTTP traffic for anomalies indicative of request/response splitting attacks is also recommended. Incorporating automated security testing, including fuzzing and static analysis focused on header injection, can help detect similar issues proactively. Finally, educating developers on secure handling of HTTP headers and the risks of CRLF injection is critical to prevent recurrence.