CVE-2026-82921: ShopEx ECShop Auth Bypass Vulnerability

CVE-2026-82921 Overview

CVE-2026-82921 is an unrestricted file upload weakness in ShopEx ECShop versions up to 2.5.1. The flaw resides in the check_img_type function of admin/pack.php. An attacker can manipulate the pack_img argument to bypass file type validation and upload arbitrary content to the server. The issue is remotely exploitable and a public exploit is available. According to VulDB, the vendor was contacted about this disclosure but did not respond. The vulnerability is classified under CWE-284: Improper Access Control.

Critical Impact
Remote attackers can bypass image type checks in admin/pack.php to upload arbitrary files, potentially staging follow-on code execution against ECShop deployments.

Affected Products

ShopEx ECShop 2.0.x
ShopEx ECShop 2.5.0
ShopEx ECShop 2.5.1

Discovery Timeline

2026-08-31 - CVE-2026-82921 published to NVD
2026-09-01 - Last updated in NVD database

Technical Details for CVE-2026-82921

Vulnerability Analysis

The weakness affects the check_img_type function inside admin/pack.php, which is responsible for validating the type of files supplied through the pack_img parameter. Because the validation is insufficient, an attacker can submit a crafted request that bypasses the check and writes an arbitrary file into the ECShop installation. Public exploit code has been released, lowering the bar for opportunistic attacks against exposed ECShop instances.

Root Cause

The root cause is improper access control combined with weak file type verification in check_img_type. Rather than enforcing content-based validation or a strict allowlist, the routine can be tricked by attacker-controlled input in the pack_img argument. This allows content that is not a legitimate image to be accepted and stored by the application.

Attack Vector

Exploitation occurs over the network with no user interaction required. An attacker sends a manipulated request targeting admin/pack.php with a crafted pack_img value. The affected function fails to reject the payload, and the file is written to a location reachable by the web server. Depending on server configuration, the uploaded file can be leveraged for further compromise. The exploit has been made public, according to VulDB references.

No verified proof-of-concept code is reproduced here. See the VulDB entry for CVE-2026-82921 and the VulDB vulnerability record #397301 for technical details.

Detection Methods for CVE-2026-82921

Indicators of Compromise

Unexpected files, especially non-image content, written under ECShop upload or pack directories after requests to admin/pack.php.
POST requests to admin/pack.php containing a pack_img parameter with non-image MIME types, double extensions, or script content.
Web server access logs showing successful requests to admin/pack.php from untrusted or unauthenticated sources.

Detection Strategies

Inspect web server and application logs for anomalous access patterns to admin/pack.php, correlating with subsequent requests to newly created files.
Deploy web application firewall rules that inspect uploads to ECShop administrative endpoints and reject content whose magic bytes do not match declared image types.
File integrity monitoring on the ECShop web root to alert on new executable or script files appearing in upload directories.

Monitoring Recommendations

Alert on any process spawned by the PHP interpreter from within ECShop upload directories, which typically indicates webshell execution.
Monitor outbound network connections originating from the ECShop web server to detect post-exploitation callbacks.
Track authentication events to the ECShop admin panel and correlate failed and successful logins with admin/pack.php activity.

How to Mitigate CVE-2026-82921

Immediate Actions Required

Restrict access to admin/pack.php and the entire ECShop administrative interface to trusted IP ranges or via VPN until a vendor patch is available.
Audit ECShop upload and pack directories for unexpected files and remove any that cannot be attributed to legitimate administrator activity.
Rotate ECShop administrator credentials and review admin account provisioning for unauthorized additions.

Patch Information

No vendor patch has been published. VulDB notes that the vendor was contacted early about this disclosure but did not respond. Organizations running ShopEx ECShop 2.5.1 or earlier should evaluate migrating to a maintained e-commerce platform or applying compensating controls until an official fix is released. Track updates via the VulDB CVE-2026-82921 record.

Workarounds

Disable or remove admin/pack.php if the packaging feature is not required in your deployment.
Enforce server-side content validation by configuring the web server to deny execution of PHP and other scripts within ECShop upload directories.
Place ECShop behind a web application firewall with rules that reject uploads whose file content does not match a strict image allowlist.

bash

# Example nginx configuration to prevent script execution in upload directories
location ~ ^/(upload|images|pack)/.*\.(php|phtml|phar|pl|py|jsp|sh|cgi)$ {
    deny all;
    return 403;
}