CVE-2025-4035 is a medium-severity vulnerability identified in the libsoup library used by Red Hat Enterprise Linux 10. Libsoup is a GNOME HTTP client library that handles HTTP requests and responses, including cookie management. The flaw arises from improper handling of case sensitivity when processing cookies. Specifically, libsoup clients incorrectly allow cookies to be set for public suffix domains if the domain name contains at least two components and includes an uppercase character. Public suffix domains are top-level domains or domain suffixes under which multiple organizations can register subdomains (e.g., .com, .co.uk). Normally, browsers and HTTP clients enforce restrictions preventing cookies from being set on these public suffixes to avoid cookie scope violations and security issues. However, due to this vulnerability, an attacker-controlled malicious website can bypass these protections by exploiting the case sensitivity flaw, setting cookies for domains it does not own. This can lead to integrity issues such as session fixation, where an attacker forces a user’s session identifier to a known value, potentially enabling session hijacking or unauthorized access. The vulnerability does not impact confidentiality or availability directly but compromises the integrity of session management. The CVSS score is 4.3 (medium), reflecting that the attack vector is network-based, requires no privileges, but does require user interaction (e.g., visiting a malicious website). There is no indication of known exploits in the wild yet, and no patches or mitigations are explicitly linked in the provided data. The flaw is specific to Red Hat Enterprise Linux 10’s libsoup implementation, which is widely used in GNOME-based environments and applications relying on this library for HTTP communications.

For European organizations, especially those using Red Hat Enterprise Linux 10 in desktop or server environments with GNOME or applications relying on libsoup, this vulnerability poses a risk to session integrity. Attackers could exploit this flaw by tricking users into visiting malicious websites that set cookies improperly scoped to public suffix domains, potentially enabling session fixation attacks. This could lead to unauthorized access to web applications or services that rely on cookie-based session management, impacting internal corporate portals, webmail, or other browser-based tools. While the vulnerability does not directly expose sensitive data or cause service outages, the integrity compromise could facilitate further attacks such as privilege escalation or data manipulation. Organizations with high reliance on Red Hat Enterprise Linux 10 in user-facing environments or internal web services should be particularly cautious. The risk is heightened in sectors with sensitive session-based applications, such as finance, government, and critical infrastructure, common in Europe. However, the requirement for user interaction and the medium severity score suggest the threat is moderate but should not be ignored.

1. Apply official patches from Red Hat as soon as they become available to address the libsoup cookie handling flaw. Monitor Red Hat security advisories closely. 2. In the interim, consider disabling or restricting the use of libsoup-based applications or components that handle HTTP cookies, especially in environments where session integrity is critical. 3. Implement web application security measures such as HttpOnly and Secure cookie flags, SameSite attributes, and robust session management to reduce the impact of session fixation attempts. 4. Educate users about the risks of visiting untrusted websites and phishing attacks that could trigger malicious cookie setting. 5. Employ network-level protections such as web filtering and DNS filtering to block access to known malicious domains. 6. Conduct security testing and code review of internal applications relying on libsoup or similar libraries to identify and remediate session management weaknesses. 7. Monitor logs and alerts for unusual cookie-setting behavior or session anomalies that could indicate exploitation attempts.