CVE-2026-90500: lenve vhr Avatar Upload RCE Vulnerability

CVE-2026-90500 Overview

CVE-2026-90500 is an unrestricted file upload vulnerability in lenve vhr version 1.0-SNAPSHOT. The flaw resides in the FastDFSUtils.upload function invoked through the /hr/userface endpoint, which handles avatar image uploads. Attackers can manipulate the File argument to bypass upload restrictions and place arbitrary files on the server. The vendor was contacted before public disclosure but did not respond. Public exploit details are available, increasing the likelihood of opportunistic abuse against exposed instances. The weakness is classified under [CWE-284: Improper Access Control].

Critical Impact
Authenticated remote attackers can upload arbitrary files through the avatar upload endpoint, providing a foothold for further compromise of the vhr application server.

Affected Products

lenve vhr 1.0-SNAPSHOT
Component: Avatar Upload (/hr/userface)
Function: FastDFSUtils.upload

Discovery Timeline

2026-09-13 - CVE-2026-90500 published to the National Vulnerability Database (NVD)
2026-09-14 - Last updated in NVD database

Technical Details for CVE-2026-90500

Vulnerability Analysis

The vulnerability exists in the avatar upload workflow of lenve vhr, a human resources management application. The /hr/userface endpoint accepts multipart file uploads and forwards them to the FastDFSUtils.upload helper. The helper does not validate the file type, extension, or content of the submitted File parameter before writing it to the FastDFS storage backend.

Because the endpoint enforces no allowlist of permitted MIME types or extensions, attackers can submit executable content disguised as an avatar image. The uploaded resource is then reachable through the distributed file system, allowing attackers to reference their payload from other application contexts. Exploitation requires low-privilege authentication and can be performed remotely over the network.

Root Cause

The root cause is improper access control on the upload handler, mapped to [CWE-284]. The FastDFSUtils.upload routine trusts the caller-supplied filename and byte stream without server-side validation. No checks constrain the file extension, magic bytes, size, or storage path, and no authorization boundary restricts which authenticated roles may upload arbitrary content.

Attack Vector

An authenticated user submits a crafted HTTP POST request to /hr/userface containing a malicious file in the File multipart parameter. The application accepts the payload and stores it in FastDFS, returning a reference URL. Attackers can then request the stored object to trigger downstream effects, including hosting malicious content, staging secondary payloads, or attempting execution if the storage tier serves the file with an interpretable content type. See the GitHub VHR-VULN-005 Advisory and VulDB CVE-2026-90500 Details for reproduction steps.

Detection Methods for CVE-2026-90500

Indicators of Compromise

Unexpected file types (.jsp, .php, .html, .svg with scripts) stored in the FastDFS avatar path.
HTTP POST requests to /hr/userface with multipart File parameters larger than typical avatar images.
Newly created accounts followed immediately by avatar upload activity from the same source IP.
Outbound connections initiated from the vhr application host to attacker-controlled infrastructure after upload events.

Detection Strategies

Inspect web server access logs for POST requests to /hr/userface and correlate with the response status and stored object URLs.
Baseline expected avatar upload sizes and MIME types, and alert on deviations such as scripts or archives.
Deploy WAF rules that inspect multipart uploads to the endpoint and reject non-image content types or files failing magic-byte checks.

Monitoring Recommendations

Audit FastDFS storage buckets for objects with executable or script extensions.
Forward vhr application and FastDFS access logs to a central SIEM for retention and correlation.
Monitor authentication logs for credential stuffing or newly created low-privilege accounts that subsequently upload files.

How to Mitigate CVE-2026-90500

Immediate Actions Required

Restrict access to the /hr/userface endpoint at the network or reverse proxy layer until a fix is available.
Enforce strict server-side allowlisting of image MIME types and extensions on all upload handlers.
Rotate credentials for any low-privilege accounts that may have been abused and review recent uploads for malicious content.
Isolate the FastDFS storage tier so uploaded objects are served with a non-executable content type.

Patch Information

At the time of publication, the vendor has not responded to disclosure and no official patch is available. Track the VulDB Vulnerability #403088 entry and the upstream lenve vhr repository for future updates. Organizations that maintain their own fork should add extension allowlisting, magic-byte validation, size limits, and authorization checks to FastDFSUtils.upload before redeploying.

Workarounds

Place the vhr application behind a WAF that inspects /hr/userface uploads and blocks non-image payloads.
Reconfigure FastDFS or the fronting web server to serve stored files with Content-Type: application/octet-stream and Content-Disposition: attachment to prevent inline execution.
Disable avatar uploads for user roles that do not require the feature by adjusting application-level authorization rules.

bash

# Example Nginx snippet to block non-image uploads to the vulnerable endpoint
location /hr/userface {
    client_max_body_size 512k;
    if ($http_content_type !~* "^multipart/form-data") { return 403; }
    # Forward to upstream only after WAF inspection
    proxy_pass http://vhr_backend;
}