CVE-2025-7626: Kkfileviewofficeedit Path Traversal Flaw

CVE-2025-7626 Overview

CVE-2025-7626 is a path traversal vulnerability in YiJiuSmile kkFileViewOfficeEdit, an open-source office document preview and editing tool. The flaw resides in the onlinePreview function exposed at the /onlinePreview endpoint. An attacker can manipulate the url argument to traverse directories and access files outside the intended preview scope. The product does not use versioning, so affected and unaffected releases cannot be enumerated; the issue is tied to commit 5fbc57c48e8fe6c1b91e0e7995e2d59615f37abd and earlier states of the repository. The exploit details have been publicly disclosed, and the attack can be launched remotely over the network with low privileges.

Critical Impact

Remote attackers with low privileges can read files outside the intended preview directory by manipulating the url parameter on /onlinePreview, enabling disclosure of application files and configuration data [CWE-22].

Affected Products

• YiJiuSmile kkFileViewOfficeEdit up to commit 5fbc57c48e8fe6c1b91e0e7995e2d59615f37abd
• Component: onlinePreview function in the /onlinePreview endpoint
• All deployments without versioning, distributed via the public GitHub repository

Discovery Timeline

• 2025-07-14 - CVE-2025-7626 published to NVD
• 2026-04-29 - Last updated in NVD database

Technical Details for CVE-2025-7626

Vulnerability Analysis

The vulnerability is a classic path traversal issue [CWE-22] in a file preview handler. The /onlinePreview route accepts a url parameter that determines which document the server fetches or reads for rendering. The handler fails to canonicalize the resolved path and does not constrain it to an allowed base directory. As a result, attacker-controlled traversal sequences such as ../ redirect the file access primitive to arbitrary locations on the host file system. Because the product targets office document preview workflows, the service often runs with permissions sufficient to read sensitive application files, including configuration, credentials, and uploaded user content.

The scope of impact is limited to confidentiality of files readable by the service account. The CVSS 4.0 vector reflects network reach with low attack complexity and low privileges required, no user interaction, and low confidentiality impact with no integrity or availability effect.

Root Cause

The root cause is missing input validation and path canonicalization on the url argument before it is used to locate the document to preview. The application trusts caller-supplied path segments and does not enforce a deny list for traversal tokens or a strict allow list of preview roots. Without normalization of the resolved path against an expected base directory, the file-access call resolves outside the intended location.

Attack Vector

The attacker sends an HTTP request to /onlinePreview with a crafted url parameter containing relative traversal sequences or absolute paths that resolve to sensitive files. Authentication requirements are low, and no user interaction is needed. Since the product lacks versioning, deployments built directly from the upstream repository remain exposed until maintainers ship a corrected path-handling routine. Public proof-of-concept details are referenced in the GitHub Issue Discussion and the VulDB entry #316327.

Detection Methods for CVE-2025-7626

Indicators of Compromise

• HTTP requests to /onlinePreview containing ../, ..\, URL-encoded variants (%2e%2e%2f), or absolute paths in the url parameter
• Access log entries showing the preview service reading files outside the configured document root, such as /etc/passwd, application config files, or credential stores
• Outbound requests initiated by the preview process to attacker-controlled hosts when url references remote schemes

Detection Strategies

• Inspect web server and reverse-proxy logs for url parameter values containing traversal patterns and decode multi-layer URL encodings before matching
• Deploy a WAF rule that blocks or alerts on path traversal signatures targeting /onlinePreview
• Correlate process-level file-read events from the kkFileViewOfficeEdit service with access paths outside the configured preview directory

Monitoring Recommendations

• Enable verbose request logging on the /onlinePreview endpoint, capturing full query strings for forensic review
• Alert on the preview service accessing operating system or application configuration files, which is not expected during normal use
• Track unusual spikes in /onlinePreview traffic from a single source, which often indicate automated enumeration of file paths

How to Mitigate CVE-2025-7626

Immediate Actions Required

• Restrict network exposure of /onlinePreview to trusted internal networks or place it behind authenticated reverse-proxy access
• Add a WAF or upstream filter that rejects url parameter values containing ../, ..\, URL-encoded traversal sequences, or absolute file paths
• Run the kkFileViewOfficeEdit service under a dedicated low-privilege account with file system access limited to the preview document directory

Patch Information

No official patch release is published at this time. The product does not use versioning, so remediation requires monitoring the upstream repository for a fix to the onlinePreview handler. Track the GitHub Issue Discussion for maintainer updates and apply commits that introduce path canonicalization and base-directory enforcement on the url argument.

Workarounds

• Implement a server-side allow list that maps client-supplied identifiers to preconfigured file paths, removing direct caller control over file locations
• Canonicalize the resolved path and verify it begins with the intended document root before opening the file
• Apply mandatory access controls such as AppArmor or SELinux profiles that confine the service to its document directory

# Example reverse-proxy filter (nginx) to block traversal patterns on /onlinePreview
location /onlinePreview {
    if ($args ~* "(\.\./|\.\.\\|%2e%2e%2f|%2e%2e/|/%2e%2e)") {
        return 403;
    }
    proxy_pass http://kkfileview_backend;
}