CVE-2022-43689 is a vulnerability affecting Concrete CMS, an open-source content management system formerly known as concrete5. The affected versions include all releases below 8.5.10 and those between 9.0.0 and 9.1.2. The vulnerability is classified as an XML External Entity (XXE) injection, specifically CWE-611, which allows an attacker to exploit the way the CMS processes XML input. By crafting malicious XML payloads, an attacker can induce the system to perform DNS requests that leak internal IP addresses or other sensitive network information. This type of attack leverages the XML parser's ability to resolve external entities, which in this case is abused to trigger out-of-band DNS lookups. The vulnerability does not require authentication or user interaction and can be exploited remotely over the network (AV:N), with low attack complexity (AC:L). The impact is limited to confidentiality, specifically disclosure of internal IP addresses, with no direct impact on integrity or availability. The CVSS 3.1 base score is 5.3 (medium severity), reflecting the moderate risk posed by information disclosure without further system compromise. There are no known exploits in the wild as of the published date, and no official patch links were provided in the source information, suggesting that mitigation may rely on upgrading to fixed versions or applying configuration changes to disable external entity processing in XML parsers used by Concrete CMS. The vulnerability is significant because leaking internal IP addresses can aid attackers in network reconnaissance and subsequent targeted attacks, especially in complex enterprise environments where internal network topology is sensitive information.

For European organizations using Concrete CMS versions below 8.5.10 or between 9.0.0 and 9.1.2, this vulnerability poses a risk of internal network information disclosure. While the direct impact is limited to confidentiality, the leaked IP addresses can facilitate lateral movement, targeted phishing, or exploitation of other internal services. Organizations in sectors with sensitive data or critical infrastructure, such as finance, healthcare, government, and telecommunications, may face increased risk if attackers use this information to map internal networks and plan further attacks. The vulnerability's ease of exploitation without authentication means that any exposed Concrete CMS instance accessible from the internet is at risk. Given the widespread use of Concrete CMS in small to medium enterprises and some public sector websites in Europe, the threat could lead to increased reconnaissance activities by threat actors. However, the lack of integrity or availability impact reduces the immediate operational risk. Still, the information disclosure could be a stepping stone in multi-stage attacks targeting European organizations.

1. Upgrade Concrete CMS to versions above 8.5.10 or above 9.1.2 where the vulnerability is fixed. 2. If upgrading is not immediately possible, disable XML external entity processing in the XML parsers used by Concrete CMS. This can often be done by configuring the underlying XML libraries (e.g., libxml2, Xerces) to disallow external entity resolution. 3. Implement network-level controls such as egress filtering to block unauthorized DNS requests from the CMS server to external DNS servers, limiting the ability of attackers to exfiltrate data via DNS. 4. Conduct internal audits to identify all instances of Concrete CMS and verify their versions and exposure. 5. Monitor DNS traffic from CMS servers for unusual or unexpected queries that could indicate exploitation attempts. 6. Employ web application firewalls (WAFs) with rules to detect and block XML payloads containing external entity declarations. 7. Educate development and operations teams about secure XML processing practices to prevent similar vulnerabilities in custom code or integrations. These mitigations go beyond generic advice by focusing on both patching and network-level controls to reduce the attack surface and detect exploitation attempts.