CVE-2026-25869 identifies a path traversal vulnerability (CWE-22) in MiniGal Nano, a lightweight photo gallery application, affecting versions 0.3.5 and prior. The vulnerability resides in the index.php script, where the 'dir' parameter is used to specify directories within the photos folder. The application attempts to prevent directory traversal attacks by removing dot-dot ('..') sequences from user input. However, this sanitization is insufficient and can be bypassed using crafted directory patterns that evade the simple string replacement, allowing attackers to traverse outside the intended photos directory. By exploiting this flaw, an attacker can cause the application to enumerate and display image files from arbitrary filesystem locations readable by the web server. This leads to unintended information disclosure, potentially exposing sensitive files or data stored on the server. The vulnerability requires no authentication or user interaction, and the attack vector is network-based, making it remotely exploitable. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N) reflects a network attack with low complexity, no privileges or user interaction needed, and limited confidentiality impact. No patches or fixes have been released at the time of publication, and no known exploits are currently active in the wild. The issue highlights the risks of insufficient input validation and the importance of robust path sanitization in web applications handling user-supplied file paths.

The primary impact of this vulnerability is unintended information disclosure. Attackers can access and enumerate image files outside the intended photos directory, potentially exposing sensitive or confidential files readable by the web server. This could include configuration files, backups, or other data stored on the server that should not be publicly accessible. While the vulnerability does not allow code execution or modification of files, the exposure of sensitive information can facilitate further attacks such as credential theft, reconnaissance, or social engineering. Organizations using MiniGal Nano in publicly accessible environments are at risk of data leakage, which could damage reputation, violate privacy regulations, or lead to compliance issues. Since no authentication is required, any remote attacker can exploit this vulnerability, increasing the attack surface. The medium CVSS score reflects the moderate severity due to limited confidentiality impact and no direct integrity or availability effects. However, the scope of affected systems is limited to those running vulnerable MiniGal Nano versions, which may be used by small to medium websites or personal galleries.

To mitigate this vulnerability, organizations should first verify if they are running MiniGal Nano version 0.3.5 or earlier and consider upgrading to a fixed version once available. In the absence of an official patch, administrators can implement temporary mitigations such as: 1) Restricting web server file system permissions to limit the directories readable by the web server user, ensuring sensitive directories are inaccessible. 2) Employing web application firewalls (WAFs) to detect and block suspicious requests containing directory traversal patterns or unusual 'dir' parameter values. 3) Applying input validation and sanitization at the web server or reverse proxy level to reject requests with directory traversal attempts. 4) Isolating the MiniGal Nano application in a container or sandbox environment to minimize exposure. 5) Monitoring web server logs for anomalous access patterns targeting the 'dir' parameter to detect exploitation attempts early. Developers should review and improve the path sanitization logic to correctly handle all traversal patterns, possibly by resolving real paths and enforcing strict directory whitelisting. Finally, organizations should maintain regular backups and conduct security audits to identify and remediate similar vulnerabilities.