CVE-2024-1246 is a reflected Cross-Site Scripting (XSS) vulnerability identified in Concrete CMS versions 9.0.0 up to but not including 9.2.5. The vulnerability arises from improper input validation (CWE-20) in the Image URL Import feature, which allows an authenticated administrator to supply maliciously crafted input that is not sufficiently sanitized. When an administrator imports an image using a specially crafted URL, the malicious payload can be reflected and executed in the browsers of users visiting the affected website. This reflected XSS attack vector requires administrator privileges to inject the malicious code and also requires user interaction, as the malicious script executes in the context of the website user’s browser. The vulnerability does not affect Concrete CMS versions prior to 9.0.0 or versions 9.2.5 and later, where presumably input validation has been improved. The vendor’s internal CVSS v3 vector assessment rates this vulnerability as medium severity (CVSS score 2.0) with the following characteristics: network attack vector (AV:N), high attack complexity (AC:H), high privileges required (PR:H), user interaction required (UI:R), unchanged scope (S:U), low confidentiality impact (C:L), no integrity or availability impact (I:N/A:N). There are no known exploits in the wild at the time of publication, and no official patches have been linked yet. This vulnerability primarily threatens the confidentiality of user data by enabling script execution in users’ browsers, which could be leveraged for session hijacking, phishing, or other client-side attacks. However, the requirement for administrator privileges to inject the payload and the need for user interaction limit the ease of exploitation and overall impact.

For European organizations using Concrete CMS versions 9.0.0 through 9.2.4, this vulnerability poses a risk primarily to the confidentiality of their website users. An attacker with administrator access could inject malicious scripts that execute in visitors’ browsers, potentially leading to theft of session cookies, user credentials, or other sensitive information. This could damage the organization's reputation, lead to data breaches, or facilitate further attacks such as phishing or drive-by downloads. However, since exploitation requires administrator privileges, the threat is largely internal or from compromised administrator accounts. The impact on integrity and availability of the CMS or hosted services is minimal. European organizations with public-facing websites built on Concrete CMS, especially those handling sensitive user data or operating in regulated sectors like finance, healthcare, or government, should be particularly cautious. The reflected XSS could also be used to bypass Content Security Policies if improperly configured, increasing risk. Given the medium severity and attack complexity, the threat is moderate but should not be ignored, especially in environments with multiple administrators or where administrator accounts may be less strictly controlled.

1. Upgrade Concrete CMS installations to version 9.2.5 or later as soon as a patch is available to ensure the vulnerability is addressed at the source. 2. Until patching is possible, restrict administrator access strictly to trusted personnel and enforce strong authentication mechanisms such as multi-factor authentication (MFA) to reduce the risk of account compromise. 3. Implement rigorous input validation and output encoding on all user-supplied data, particularly in custom plugins or extensions that interact with the Image URL Import feature. 4. Employ Content Security Policy (CSP) headers to restrict the execution of inline scripts and reduce the impact of reflected XSS attacks. 5. Monitor administrator activities and audit logs for unusual image import operations or suspicious URL inputs. 6. Educate administrators about the risks of importing images from untrusted sources and the importance of validating URLs before use. 7. Conduct regular security assessments and penetration testing focused on CMS components to detect similar vulnerabilities proactively. 8. Consider deploying Web Application Firewalls (WAFs) with rules tuned to detect and block reflected XSS payloads targeting the Image URL Import functionality.