CVE-2023-49082 is a vulnerability classified under CWE-93 (Improper Neutralization of CRLF Sequences) found in aiohttp, a widely used asynchronous HTTP client/server framework for Python's asyncio library. The vulnerability arises due to insufficient validation of the HTTP method and version fields in incoming requests. Specifically, if an attacker can control the HTTP method (e.g., GET, POST) of a request, they can inject CRLF (carriage return and line feed) sequences, which enables them to insert arbitrary HTTP headers or even craft entirely new HTTP requests. This can facilitate HTTP request smuggling attacks, where malicious requests bypass security controls or interfere with backend processing. The vulnerability only manifests if the attacker can influence the HTTP method; control over the HTTP version further amplifies the risk by enabling more extensive request manipulation. The issue affects aiohttp versions earlier than 3.9.0, with the vendor releasing a patch in version 3.9.0 to properly sanitize and validate these inputs. The CVSS v3.1 base score is 5.3 (medium), reflecting the network attack vector, low attack complexity, no privileges or user interaction required, and impact limited to integrity. No known exploits have been reported in the wild as of the publication date. This vulnerability is particularly relevant for applications exposing HTTP endpoints using aiohttp, including web servers, APIs, and microservices, where untrusted input might influence HTTP request construction.

For European organizations, the impact of CVE-2023-49082 primarily concerns the integrity of HTTP communications handled by aiohttp-based services. Successful exploitation could allow attackers to inject malicious headers or smuggle requests, potentially bypassing security controls such as web application firewalls, authentication mechanisms, or input validation layers. This could lead to unauthorized actions, session fixation, cache poisoning, or other downstream attacks impacting business logic. While confidentiality and availability are not directly affected, the integrity compromise can facilitate further exploitation or data manipulation. Organizations relying on aiohttp for critical infrastructure, financial services, healthcare, or government applications may face increased risk due to the sensitive nature of their data and regulatory requirements under GDPR. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially given the ease of exploitation and network accessibility. European entities with extensive Python development or microservice architectures using aiohttp are particularly exposed.

The primary mitigation is to upgrade all aiohttp deployments to version 3.9.0 or later, where the vulnerability has been patched. Organizations should audit their codebases and dependencies to identify any usage of vulnerable aiohttp versions. For environments where immediate upgrading is not feasible, implementing strict input validation and filtering at the network perimeter or application gateway can help mitigate injection attempts. Deploying web application firewalls (WAFs) configured to detect and block CRLF injection patterns and anomalous HTTP methods may reduce risk. Additionally, monitoring HTTP traffic for unusual header insertions or malformed requests can provide early detection. Developers should avoid allowing untrusted input to control HTTP methods or versions. Security teams should incorporate this vulnerability into their vulnerability management and patching cycles and conduct penetration testing focused on HTTP request smuggling scenarios. Finally, ensure logging and alerting mechanisms are in place to detect exploitation attempts.