CVE-2025-58618 is a DOM-based Cross-site Scripting (XSS) vulnerability identified in the Jonathan Jernigan Pie Calendar application, affecting versions up to 1.2.8. The vulnerability arises from improper neutralization of input during web page generation, classified under CWE-79. Specifically, the application fails to adequately sanitize or encode user-supplied input before incorporating it into the Document Object Model (DOM), allowing malicious scripts to be executed in the context of the victim's browser. This type of XSS is client-side and occurs when the web application uses unsafe JavaScript methods to process input data, leading to script injection without server-side validation. The CVSS v3.1 base score is 6.5, indicating a medium severity level. The vector details (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L) show that the attack can be launched remotely over the network with low attack complexity, requires privileges (PR:L) and user interaction (UI:R), and impacts confidentiality, integrity, and availability to a limited extent. The scope is changed (S:C), meaning the vulnerability affects components beyond the initially vulnerable component. No known exploits are currently reported in the wild, and no patches or fixes have been linked yet. The vulnerability could be exploited by tricking authenticated users with some privileges into interacting with crafted malicious links or content that triggers the XSS payload, potentially leading to session hijacking, data theft, or unauthorized actions within the application context.

For European organizations using the Jonathan Jernigan Pie Calendar, this vulnerability poses a moderate risk. Since the vulnerability requires user interaction and some level of privileges, the threat is more significant in environments where the calendar is integrated into internal or collaborative platforms with authenticated users. Exploitation could lead to unauthorized disclosure of sensitive calendar data, manipulation of calendar entries, or execution of malicious scripts that could pivot to further attacks within the corporate network. The confidentiality, integrity, and availability of calendar data could be compromised, impacting business operations, especially in sectors relying heavily on scheduling and coordination such as finance, healthcare, and government. Additionally, if the calendar is embedded or linked within intranet portals or widely used web applications, the attack surface increases. The lack of a patch means organizations must rely on mitigations until an official fix is released. Given the medium severity and the requirement for user interaction, the overall impact is moderate but should not be underestimated in environments with high-value targets or sensitive scheduling information.

To mitigate this vulnerability effectively, European organizations should implement the following specific measures: 1) Apply strict Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of DOM-based XSS. 2) Employ input validation and output encoding on all user-supplied data before it is processed or rendered by client-side scripts, even if the application does not currently do so. 3) Restrict user privileges within the Pie Calendar application to the minimum necessary to reduce the risk posed by compromised accounts. 4) Educate users about the risks of clicking on suspicious links and the importance of verifying URLs before interaction, especially in authenticated sessions. 5) Monitor web traffic and application logs for unusual activity that may indicate exploitation attempts. 6) If possible, isolate the Pie Calendar application within a sandboxed environment or use web application firewalls (WAFs) with rules targeting XSS payload patterns. 7) Stay alert for vendor updates or patches and plan for timely deployment once available. 8) Consider alternative calendar solutions if the risk is deemed unacceptable and no patch timeline is provided.