CVE-2026-22779 is a vulnerability classified under CWE-113, involving improper neutralization of CRLF (Carriage Return Line Feed) sequences in HTTP headers within the BlackSheep asynchronous web framework's HTTP Client component. BlackSheep is a Python-based framework designed for event-driven web applications. The flaw exists in versions prior to 2.4.6, where the HTTP Client fails to validate or sanitize headers properly, allowing attackers to inject CRLF sequences. This can enable HTTP request/response splitting attacks, where an attacker can manipulate the HTTP request by injecting additional headers or even crafting entirely new HTTP requests. The vulnerability arises specifically when developers pass unsanitized user input directly into HTTP headers, which is a misuse scenario rather than a server-side flaw. The server-side response handling is not vulnerable because BlackSheep delegates response header processing to an underlying ASGI server that properly handles header validation. The CVSS 4.0 vector indicates the attack is network-based (AV:N), requires low attack complexity (AC:L), no privileges (PR:N), no user interaction (UI:N), and partial impact on confidentiality, integrity, and availability (SI:L), with scope limited to the vulnerable component (SC:L). The vulnerability was published on January 14, 2026, and no known exploits have been reported. The fix is included in BlackSheep version 2.4.6, which adds proper header validation to prevent CRLF injection.

For European organizations, this vulnerability poses risks primarily to applications that use BlackSheep's HTTP Client for making outbound HTTP requests and that incorporate unsanitized user input into HTTP headers. Successful exploitation could allow attackers to perform HTTP request splitting, leading to various downstream attacks such as cache poisoning, cross-site scripting (XSS), session fixation, and web cache deception. These attacks can compromise user confidentiality and integrity of communications, potentially enabling data theft or session hijacking. Although the vulnerability does not affect the server response headers, the client-side injection can still disrupt application logic or security controls relying on HTTP headers. Organizations in sectors with high web application usage, such as finance, healthcare, and government, may face increased risk due to the sensitivity of their data and regulatory requirements like GDPR. The lack of known exploits reduces immediate risk, but the ease of exploitation and network accessibility mean attackers could develop exploits rapidly if the vulnerability becomes widely known. Failure to patch could lead to reputational damage, regulatory fines, and operational disruptions.

European organizations should immediately upgrade BlackSheep to version 2.4.6 or later to ensure the vulnerability is patched. Developers must audit their codebases to identify any instances where user input is incorporated into HTTP headers without proper sanitization or validation. Implement strict input validation and sanitization routines to neutralize CRLF characters before including user data in headers. Employ security code reviews and automated static analysis tools to detect unsafe header manipulations. Additionally, consider implementing Web Application Firewalls (WAFs) with rules to detect and block HTTP header injection attempts. Monitor application logs for unusual HTTP header patterns indicative of exploitation attempts. Educate developers on secure coding practices related to HTTP header construction. Finally, maintain an inventory of applications using BlackSheep to prioritize patching and risk assessment efforts.