CVE-2026-67678: DocSys File Upload RCE Vulnerability

CVE-2026-67678 Overview

CVE-2026-67678 is an unrestricted file upload vulnerability in RainyGao DocSys version 2.02.80. The flaw allows remote, unauthenticated attackers to upload arbitrary files to the document management application. Successful exploitation leads to arbitrary code execution on the underlying server. The weakness is categorized under CWE-434: Unrestricted Upload of File with Dangerous Type. DocSys is an open-source document management system maintained on GitHub, commonly deployed for enterprise file sharing and collaboration.

Critical Impact
Remote attackers can upload malicious files without authentication and execute arbitrary code on DocSys 2.02.80 servers, resulting in full system compromise.

Affected Products

RainyGao DocSys version 2.02.80
Earlier DocSys releases sharing the vulnerable upload handler (per vendor issue tracker)
Deployments exposing the DocSys web interface to untrusted networks

Discovery Timeline

2026-08-17 - CVE-2026-67678 published to the National Vulnerability Database (NVD)
2026-08-18 - Last updated in NVD database
2026-08-23 - EPSS score recorded at 0.587% (45.39 percentile)

Technical Details for CVE-2026-67678

Vulnerability Analysis

The vulnerability resides in the file upload functionality of DocSys 2.02.80. The application accepts uploaded files without enforcing sufficient validation on file type, extension, or content. An attacker submits a crafted HTTP request containing an executable payload, such as a server-side script matching the deployed runtime. The web server then processes the uploaded file when the attacker requests its URL, executing attacker-controlled code in the context of the DocSys process. The attack requires no authentication, no user interaction, and is reachable across the network.

Root Cause

The root cause is unrestricted upload of files with dangerous types [CWE-434]. The upload handler fails to validate file extensions against an allowlist, does not verify MIME type or magic bytes, and stores files in a directory reachable by the web server. These conditions permit adversaries to place scripts inside a location where they are interpreted as executable code. Additional details are documented in the GitHub CVE writeup and DocSys Issue #49.

Attack Vector

An unauthenticated remote attacker sends a POST request to the DocSys upload endpoint with a malicious file payload. Because the server lacks server-side content inspection, the payload is stored intact. The attacker then issues a follow-up HTTP request to the uploaded resource path to trigger execution. This grants the adversary a foothold with the privileges of the DocSys application user, enabling data theft, lateral movement, and persistence. See the referenced GitHub CVE Documentation for reproduction details.

Detection Methods for CVE-2026-67678

Indicators of Compromise

Unexpected script files (.jsp, .jspx, .war, .php, .aspx) inside DocSys upload directories
HTTP POST requests to DocSys upload endpoints with executable extensions in the filename parameter
Outbound network connections from the DocSys application user to unknown hosts shortly after an upload event
Web shell-like process trees spawned from the DocSys or servlet container process

Detection Strategies

Inspect web server access logs for POST requests to upload endpoints followed by GET requests to newly created files
Alert on writes of executable file types to any directory served by the DocSys web root
Correlate file creation events in DocSys storage paths with process execution originating from the application server

Monitoring Recommendations

Enable file integrity monitoring on the DocSys installation directory and web root
Forward application, web server, and endpoint telemetry to a central SIEM for correlation
Baseline normal upload MIME types and extensions and alert on deviations

How to Mitigate CVE-2026-67678

Immediate Actions Required

Restrict network access to DocSys 2.02.80 instances until a vendor patch is applied
Place the application behind an authenticated reverse proxy or VPN
Audit existing upload directories for unauthorized script files and remove any suspicious artifacts
Rotate credentials and secrets accessible to the DocSys service account if compromise is suspected

Patch Information

No official vendor patch is listed in the NVD entry at time of publication. Monitor DocSys Issue #49 for maintainer updates and upgrade instructions. Track the DocSys repository release notes for a fixed version superseding 2.02.80.

Workarounds

Configure the web server to deny execution of scripts within DocSys upload directories
Enforce a strict allowlist of permitted file extensions and validate MIME types plus magic bytes server-side
Store uploaded files outside the web root and serve them through a controlled download handler
Require authentication on all upload endpoints and apply rate limiting to reduce automated abuse

bash

# Example nginx configuration to block script execution in DocSys upload paths
location ~ ^/DocSys/uploads/.*\.(jsp|jspx|php|aspx|war|sh|py)$ {
    deny all;
    return 403;
}