CVE-2025-55146 is a medium-severity vulnerability affecting multiple Ivanti products, including Ivanti Connect Secure (versions before 22.7R2.9 or 22.8R2), Ivanti Policy Secure (before 22.7R1.6), Ivanti ZTA Gateway (before 2.8R2.3-723), and Ivanti Neurons for Secure Access (before 22.8R1.4). The root cause is an unchecked return value (classified under CWE-252) in the software code, which can be exploited by a remote attacker who has authenticated administrative privileges. This unchecked return value can lead to a denial of service (DoS) condition, potentially causing the affected service to crash or become unresponsive. The vulnerability does not impact confidentiality or integrity but affects availability, as it allows disruption of service. The CVSS v3.1 base score is 4.9, reflecting a medium severity level, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), high privileges required (PR:H), no user interaction (UI:N), unchanged scope (S:U), no confidentiality or integrity impact (C:N/I:N), and high availability impact (A:H). The vulnerability was publicly disclosed on September 9, 2025, with fixes deployed on August 2, 2025. No known exploits are currently reported in the wild. The vulnerability requires an attacker to have administrative credentials, which limits the attack surface but still poses a risk if such credentials are compromised or misused. The unchecked return value likely pertains to error handling or resource management, which when triggered by an attacker, causes the service to fail, resulting in denial of service.

For European organizations, this vulnerability poses a risk primarily to the availability of critical remote access and secure gateway services provided by Ivanti products. Ivanti Connect Secure and related products are commonly used for VPN and zero-trust access solutions, which are essential for secure remote workforce connectivity and access to internal resources. A denial of service attack exploiting this vulnerability could disrupt business operations by preventing legitimate users from accessing corporate networks, potentially impacting productivity and service continuity. This is particularly significant for sectors with high reliance on remote access, such as finance, healthcare, government, and critical infrastructure. While the vulnerability requires administrative privileges, insider threats or credential compromise could enable exploitation. Additionally, denial of service incidents could be leveraged as part of a broader attack strategy to distract or delay incident response. The lack of confidentiality or integrity impact reduces the risk of data breaches directly from this vulnerability, but service disruption alone can have severe operational and reputational consequences.

European organizations using affected Ivanti products should prioritize applying the vendor-released patches (versions 22.7R2.9 or 22.8R2 for Connect Secure, 22.7R1.6 for Policy Secure, 2.8R2.3-723 for ZTA Gateway, and 22.8R1.4 for Neurons for Secure Access) as soon as possible to remediate the vulnerability. Beyond patching, organizations should enforce strict administrative access controls, including multi-factor authentication (MFA) for all admin accounts to reduce the risk of credential compromise. Regular auditing and monitoring of administrative activities can help detect suspicious behavior indicative of attempted exploitation. Network segmentation should be employed to limit exposure of Ivanti management interfaces to trusted networks only. Implementing robust incident response plans that include procedures for denial of service scenarios will help minimize operational impact. Additionally, organizations should review and harden error handling and logging configurations to ensure that failures do not cascade or cause broader service outages. Finally, maintaining up-to-date backups and redundancy for critical access infrastructure can aid in rapid recovery if a denial of service occurs.