CVE-2026-107801: Jivejdon Stored XSS Vulnerability

CVE-2026-107801 Overview

CVE-2026-107801 is a stored cross-site scripting vulnerability [CWE-79] in Jivejdon through version 5.0. The flaw lets authenticated attackers upload file attachments with an attacker-controlled Content-Type header. The UploadShowAction component serves these files inline rather than forcing a download. An attacker can upload a file declared as text/html, share the resulting link, and run JavaScript on the application's origin when other users view it.

Critical Impact
Authenticated attackers can execute arbitrary JavaScript in the browser context of any user who opens a malicious attachment link, enabling session theft, forum defacement, and account takeover within the Jivejdon origin.

Affected Products

Jivejdon versions through 5.0
UploadShowAction presentation layer component
UploadHelper attachment-handling utility

Discovery Timeline

2026-10-08 - CVE-2026-107801 published to NVD
2026-10-14 - Last updated in NVD database

Technical Details for CVE-2026-107801

Vulnerability Analysis

Jivejdon is an open-source Java forum platform. The vulnerability resides in how the application stores and serves user-uploaded attachments. During upload, the application accepts and persists the Content-Type value supplied by the client without validation against an allowlist. When a user later requests the attachment, UploadShowAction returns the file inline using that stored Content-Type.

Because the response is served from the application's own origin, any HTML or JavaScript inside the uploaded file executes with full access to the victim's session cookies, CSRF tokens, and forum DOM. The attack is persistent: once the file is uploaded, every user who follows the link triggers the payload. Attackers can harvest credentials, perform actions as the victim, or pivot to administrator accounts by targeting privileged users.

Root Cause

The root cause is improper neutralization of user-controlled input used in an HTTP response header [CWE-79]. UploadHelper.java trusts the client-provided MIME type instead of deriving it from a server-side allowlist or scanning file contents. UploadShowAction.java then writes that type directly into the Content-Type response header and serves the file inline, bypassing browser content-sniffing protections.

Attack Vector

Exploitation requires an authenticated account with permission to post attachments and limited user interaction from a victim who clicks the shared link. The attacker uploads a crafted file containing HTML or JavaScript and sets its declared Content-Type to text/html. The attacker then shares the attachment URL inside a forum post, private message, or external channel. When the victim's browser renders the response inline on the Jivejdon origin, the embedded script executes. Full technical details are available in the VulnCheck Advisory: Jivejdon XSS and the GitHub Issue Discussion #28.

Detection Methods for CVE-2026-107801

Indicators of Compromise

Attachment records in the Jivejdon database with Content-Type values of text/html, application/xhtml+xml, image/svg+xml, or other script-capable MIME types.
Web server access logs showing requests to UploadShowAction endpoints returning Content-Type: text/html for user-uploaded files.
Outbound requests from user browsers to attacker-controlled domains originating from a Jivejdon page context.

Detection Strategies

Audit the attachment store for uploaded files whose byte signatures do not match their declared MIME type.
Add web application firewall rules that inspect multipart upload requests and block disallowed Content-Type values at the perimeter.
Review HTTP responses from the attachment endpoint and alert on inline delivery of HTML, SVG, or XML content types.

Monitoring Recommendations

Forward Jivejdon application and web server logs to a centralized analytics pipeline for retention and search.
Monitor authenticated user sessions for anomalous actions following attachment views, such as unexpected profile edits or privilege changes.
Track upload volume per account and alert on bursts of attachments from newly registered users.

How to Mitigate CVE-2026-107801

Immediate Actions Required

Restrict attachment upload permissions to trusted user groups until a patched build is deployed.
Configure the reverse proxy or application to override the Content-Type on all UploadShowAction responses to a safe value such as application/octet-stream.
Add a Content-Disposition: attachment header to force download instead of inline rendering.
Review existing attachments and quarantine any files with script-capable MIME types or mismatched signatures.

Patch Information

No vendor-released patch version is referenced in the NVD entry at publication time. Monitor the GitHub Repository for Jivejdon and the referenced GitHub Issue Discussion #28 for upstream remediation. The affected code paths are documented in UploadHelper.java and UploadShowAction.java.

Workarounds

Enforce a server-side MIME allowlist that derives Content-Type from file magic bytes rather than client input.
Serve all user-uploaded content from a separate sandbox domain so stored XSS cannot access the main application origin or session cookies.
Deploy a strict Content-Security-Policy response header that blocks inline scripts and limits script sources.
Set X-Content-Type-Options: nosniff on all attachment responses to prevent browser MIME sniffing.

bash

# Nginx workaround: force safe content handling for Jivejdon attachments
location /UploadShowAction {
    add_header X-Content-Type-Options "nosniff" always;
    add_header Content-Disposition "attachment" always;
    add_header Content-Security-Policy "default-src 'none'; sandbox" always;
    proxy_hide_header Content-Type;
    add_header Content-Type "application/octet-stream" always;
    proxy_pass http://jivejdon_backend;
}