CVE-2025-69904: Linkstack Path Traversal Vulnerability

CVE-2025-69904 Overview

CVE-2025-69904 is a path traversal vulnerability affecting Linkstack v4.8.4 and earlier. The flaw allows an authenticated administrator to read arbitrary files on the underlying server by manipulating file path input parameters. Successful exploitation can expose sensitive system files, application source code, configuration files containing credentials, and other data outside the intended web application directory. The vulnerability is categorized under [CWE-22] Improper Limitation of a Pathname to a Restricted Directory.

Critical Impact
An administrator-level attacker can read arbitrary files from the host filesystem, enabling disclosure of credentials, tokens, and configuration data that can facilitate further compromise.

Affected Products

Linkstack v4.8.4
Linkstack versions prior to v4.8.4
Self-hosted Linkstack deployments exposing administrative interfaces

Discovery Timeline

2026-09-11 - CVE-2025-69904 published to NVD
2026-09-11 - Last updated in NVD database

Technical Details for CVE-2025-69904

Vulnerability Analysis

Linkstack is an open-source, self-hosted link-in-bio platform used to publish curated collections of links behind a single URL. The application exposes administrative functionality that accepts file path input. In vulnerable releases, the application fails to properly canonicalize or restrict user-supplied paths before passing them to file read operations.

An authenticated administrator can supply relative path sequences such as ../ to escape the application's intended base directory. The server then reads and returns the contents of the referenced file. Because the flaw requires administrator privileges, exploitation depends on either legitimate access, credential compromise, or a chained authentication bypass.

The impact scope extends beyond application data. Attackers can retrieve operating system files such as /etc/passwd, /etc/shadow when readable, environment files, Linkstack's .env configuration, database credentials, and API tokens. Retrieved credentials can then be used to pivot to adjacent systems or escalate control over the host.

Root Cause

The root cause is insufficient input validation on file path parameters processed by an administrative endpoint. The application concatenates user-supplied path segments with a base directory without normalizing the resulting path or verifying that the final resolved location remains within the permitted directory tree.

Attack Vector

Exploitation requires authenticated access to the Linkstack administrative interface. The attacker submits a crafted request containing directory traversal sequences in a file path parameter. The server resolves the manipulated path, reads the file, and returns its contents in the response. Refer to the CVE-2025-69904 technical writeup for reproduction details.

Detection Methods for CVE-2025-69904

Indicators of Compromise

HTTP requests to Linkstack administrative endpoints containing ../, ..\, URL-encoded %2e%2e%2f, or double-encoded traversal sequences in path parameters.
Web server access logs showing administrator-authenticated requests referencing sensitive system paths such as /etc/passwd, /etc/shadow, or application .env files.
Anomalous outbound response sizes from administrative file-handling endpoints, indicating disclosure of large or unexpected file contents.

Detection Strategies

Deploy web application firewall rules that inspect and block path traversal patterns in query strings, POST bodies, and JSON parameters submitted to Linkstack administrative routes.
Correlate administrator session activity with file read operations at the operating system level to identify reads of files outside the Linkstack installation directory.
Review authentication logs for administrator logins from unusual geolocations or IP addresses preceding suspicious file access requests.

Monitoring Recommendations

Enable verbose access logging on the reverse proxy or web server fronting Linkstack and forward logs to a centralized analytics platform.
Alert on any successful HTTP response returning file content when the request path parameter contains traversal metacharacters.
Monitor filesystem access on the Linkstack host for reads of sensitive files by the PHP or web server process user.

How to Mitigate CVE-2025-69904

Immediate Actions Required

Upgrade Linkstack to a version later than v4.8.4 once the maintainer publishes a fixed release. Track updates via the CVE-2025-69904 reference repository.
Rotate all credentials, API tokens, and secrets stored in Linkstack configuration files and the application database.
Restrict administrative interface access to trusted IP ranges using network access controls or a VPN.
Audit administrator accounts and enforce strong, unique passwords with multi-factor authentication where supported.

Patch Information

At publication time, no vendor advisory URL is listed in the CVE record. Administrators should monitor the Linkstack project repository and release notes for a patched version above v4.8.4 and apply it as soon as it is available.

Workarounds

Place Linkstack behind a reverse proxy configured to reject requests containing directory traversal sequences in path or query parameters.
Run the Linkstack PHP process under a dedicated, unprivileged user account with filesystem permissions limited to the application directory.
Deploy mandatory access controls such as AppArmor or SELinux profiles that confine the web server to the Linkstack document root.
Temporarily disable or firewall the administrative interface if immediate patching is not feasible.

bash

# Example nginx rule to block traversal patterns targeting Linkstack admin routes
location /admin/ {
    if ($request_uri ~* "(\.\./|\.\.\\|%2e%2e%2f|%2e%2e/|\.\.%2f)") {
        return 403;
    }
    proxy_pass http://linkstack_backend;
}