CVE-2024-33616 is an authentication bypass vulnerability identified in multiple Sharp Corporation multifunction printers (MFPs). The vulnerability arises because the admin authentication mechanism can be circumvented by submitting certain invalid credentials, which the device erroneously accepts as valid, thereby granting administrative privileges without proper authentication. This flaw is linked to older Sharp MFP models that have the telnet feature enabled, a legacy protocol known for weak security. Sharp Corporation has acknowledged the issue and plans to release firmware updates to remove the telnet feature and address the vulnerability. The vulnerability is classified under CWE-306 (Missing Authentication for Critical Function), indicating that critical functions are accessible without proper authentication. The CVSS v3.1 base score is 5.3, with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and impacts confidentiality (C:L) but not integrity or availability. This means an attacker can remotely exploit the vulnerability without needing credentials or user interaction, potentially gaining administrative access to the device. No public exploits have been reported yet, but the risk remains significant due to the administrative access granted. The affected product versions are not explicitly listed but are detailed in vendor advisories. The vulnerability could allow attackers to manipulate device settings, access sensitive print jobs, or pivot into internal networks if the MFP is connected to critical infrastructure.

For European organizations, this vulnerability poses a risk primarily to the confidentiality of information processed or stored on affected Sharp MFPs. Unauthorized administrative access could allow attackers to intercept or manipulate print jobs, access stored documents, or alter device configurations, potentially leading to data leakage or disruption of printing services. In environments where MFPs are integrated into broader IT or operational technology networks, attackers could leverage this access to move laterally, increasing the risk of broader network compromise. Critical sectors such as government, finance, healthcare, and manufacturing in Europe, which often rely on multifunction printers for document handling, could face operational disruptions and data breaches. The vulnerability's ease of exploitation over the network without authentication or user interaction increases the urgency for mitigation. Although no active exploits are known, the potential for future exploitation exists, especially if threat actors develop automated tools targeting these devices. The impact is heightened in organizations that have not segmented their printer networks or lack strict access controls on networked devices.

European organizations should take immediate steps to mitigate this vulnerability beyond generic advice. First, identify all Sharp MFPs in the environment, focusing on older models likely to have the telnet feature enabled. Restrict network access to these devices by implementing network segmentation and firewall rules that limit management interfaces to trusted administrators only. Disable legacy protocols such as telnet on all devices if possible, or isolate devices that require telnet on separate, secured VLANs. Monitor network traffic for unusual access attempts to MFP management interfaces. Apply firmware updates from Sharp Corporation promptly once released to remove the vulnerable telnet feature and patch the authentication bypass. In the interim, enforce strong physical security controls around MFPs to prevent local exploitation. Additionally, consider implementing network access control (NAC) solutions to ensure only authorized devices and users can communicate with MFPs. Regularly audit device configurations and access logs to detect unauthorized administrative access attempts. Training IT staff on the risks associated with networked printers and the importance of timely patching is also critical.