CVE-2025-6089 is an open redirect vulnerability identified in Astun Technology's iShare Maps version 5.4.0. The vulnerability resides in the atCheckJS.aspx file, specifically involving the manipulation of the 'ref' argument. An attacker can craft a malicious URL that leverages this parameter to redirect users to arbitrary external websites. This type of vulnerability is classified as an open redirect because the application fails to properly validate or sanitize the 'ref' parameter, allowing redirection to potentially malicious domains. The vulnerability can be exploited remotely without requiring authentication, but it does require user interaction, as the victim must click on a crafted link. The CVSS 4.0 base score is 5.3 (medium severity), reflecting that the attack vector is network-based with low attack complexity, no privileges or authentication required, but user interaction is necessary. The impact on confidentiality and availability is minimal, but there is a low integrity impact due to potential phishing or social engineering attacks that exploit the trust in the legitimate domain. The vendor has been contacted but has not responded or provided a patch, and no known exploits are currently observed in the wild, though public disclosure of the exploit details exists. This vulnerability could be leveraged by attackers to facilitate phishing campaigns, redirect users to malware-hosting sites, or bypass security filters that trust the legitimate domain, thereby increasing the risk of secondary attacks.

For European organizations using Astun Technology's iShare Maps 5.4.0, this vulnerability poses a moderate risk primarily related to user trust and phishing. Since iShare Maps is a geospatial information system often used by local governments, urban planners, and environmental agencies, exploitation could undermine user confidence and lead to targeted phishing attacks that appear to originate from trusted government or municipal sources. While the vulnerability does not directly compromise data confidentiality or system integrity, it can serve as a vector for social engineering attacks that may result in credential theft or malware infection. This is particularly concerning for organizations handling sensitive geographic or infrastructure data. The lack of vendor response and patch availability increases exposure time. Additionally, attackers could use the open redirect to bypass web filters or security controls that rely on domain reputation, increasing the likelihood of successful attacks. The impact on availability is negligible, but the reputational damage and potential downstream compromise of user systems elevate the risk profile for affected entities.

Given the absence of an official patch, European organizations should implement several targeted mitigations: 1) Employ web application firewalls (WAFs) with custom rules to detect and block requests containing suspicious or unexpected 'ref' parameter values in atCheckJS.aspx URLs. 2) Conduct user awareness campaigns emphasizing caution when clicking on links, especially those purporting to redirect from trusted iShare Maps domains. 3) Implement URL filtering and monitoring to detect and block outbound traffic to known malicious domains that could be used in redirection attacks. 4) Where feasible, restrict or proxy access to iShare Maps to internal networks or VPNs to reduce exposure to external attackers. 5) Review and harden any integration points or embedded links that use the 'ref' parameter to ensure they do not allow arbitrary redirection. 6) Monitor logs for unusual redirect patterns or spikes in traffic to external domains originating from iShare Maps. 7) Engage with Astun Technology or consider alternative geospatial platforms with active security support if remediation is delayed. These steps go beyond generic advice by focusing on the specific vulnerable parameter and usage context.