CVE-2026-1801 is a medium-severity vulnerability affecting libsoup, an HTTP client/server library used in Red Hat Enterprise Linux 10. The vulnerability arises from libsoup's soup_filter_input_stream_read_line() function, which improperly parses chunked HTTP requests by accepting malformed chunk headers that do not comply with RFC standards—specifically, it accepts lone line feed (LF) characters instead of the mandated carriage return and line feed (CRLF) sequence. This parsing flaw enables an attacker to craft malicious chunked HTTP requests that cause libsoup to interpret a single network message as multiple HTTP requests, a classic HTTP Request Smuggling attack. Such attacks can lead to desynchronization between front-end and back-end servers or proxies, potentially allowing attackers to bypass security controls, inject malicious requests, or cause information disclosure. Exploitation requires no authentication or user interaction, increasing the attack surface. Although no exploits are currently known in the wild, the vulnerability's presence in a core library used in Red Hat Enterprise Linux 10 means that any application relying on libsoup for HTTP communications could be at risk. The CVSS 3.1 base score is 5.3, reflecting network attack vector, low complexity, no privileges required, no user interaction, and limited impact on integrity but no impact on confidentiality or availability. Mitigation will require updating libsoup to a patched version that enforces strict RFC-compliant chunk header parsing.

For European organizations, this vulnerability poses a risk primarily to web-facing services and applications running on Red Hat Enterprise Linux 10 that utilize libsoup for HTTP communications. The ability to smuggle HTTP requests can lead to bypassing security controls such as web application firewalls or proxies, potentially exposing sensitive internal endpoints or enabling unauthorized actions. Information disclosure could occur if attackers manipulate request parsing to access data not intended for them. Given that exploitation requires no authentication or user interaction, attackers can remotely target vulnerable systems at scale. This could impact sectors with critical infrastructure or sensitive data, such as finance, healthcare, and government agencies in Europe. The medium severity suggests that while the vulnerability is not catastrophic, it could serve as a stepping stone for more complex attacks or lateral movement within networks. Organizations relying on Red Hat Enterprise Linux 10 in their server infrastructure should consider this vulnerability a priority for remediation to maintain compliance with European data protection regulations and cybersecurity standards.

1. Apply official patches from Red Hat as soon as they become available to update libsoup to a version that enforces strict RFC-compliant parsing of chunked HTTP requests. 2. Implement network-level filtering to detect and block malformed HTTP chunked requests, especially those containing lone LF characters instead of CRLF sequences. 3. Deploy web application firewalls (WAFs) with updated signatures capable of identifying HTTP Request Smuggling attempts targeting libsoup. 4. Conduct thorough logging and monitoring of HTTP traffic to identify anomalous request patterns indicative of smuggling attacks. 5. Review and harden proxy and load balancer configurations to ensure consistent HTTP parsing behavior across components, reducing desynchronization risks. 6. Perform security testing, including fuzzing of HTTP request parsing, to identify any residual parsing inconsistencies in the application stack. 7. Educate development and operations teams about the risks of HTTP Request Smuggling and encourage secure coding and configuration practices around HTTP handling.