CVE-2026-23843: teklifolustur_app IDOR Auth Bypass Flaw

CVE-2026-23843 Overview

CVE-2026-23843 is an Insecure Direct Object Reference (IDOR) vulnerability affecting teklifolustur_app, a web-based PHP application designed for creating, managing, and tracking client quotes. The vulnerability exists in the offer view functionality, where authenticated users can manipulate the offer_id parameter to access offers belonging to other users. This flaw stems from missing authorization checks that should verify the requested offer belongs to the currently authenticated user.

Critical Impact

Authenticated attackers can exploit this IDOR vulnerability to access sensitive quote and client data belonging to other users, potentially exposing confidential business information and customer details.

Affected Products

• teklifolustur_app versions prior to commit dd082a134a225b8dcd401b6224eead4fb183ea1c

Discovery Timeline

• 2026-01-19 - CVE CVE-2026-23843 published to NVD
• 2026-01-19 - Last updated in NVD database

Technical Details for CVE-2026-23843

Vulnerability Analysis

This vulnerability is classified under CWE-639 (Authorization Bypass Through User-Controlled Key), a common weakness where user-supplied input is used to access resources without proper authorization validation. The application fails to verify that the authenticated user has permission to view the requested offer before returning the data.

The attack surface is network-accessible and requires only low-privileged authenticated access. Successful exploitation allows attackers to read confidential information belonging to other users (high confidentiality impact) and potentially modify offer data (low integrity impact). The vulnerability requires no user interaction to exploit, making it particularly dangerous in multi-tenant environments where users share the same application instance.

Root Cause

The root cause of CVE-2026-23843 is insufficient authorization logic in the view_offer.php file. The vulnerable code retrieves offers based solely on the offer_id parameter without validating that the offer belongs to the currently authenticated user's session. This classic IDOR pattern allows any authenticated user to enumerate and access offers created by other users by simply modifying the ID parameter in requests.

Attack Vector

The attack vector is network-based, requiring an attacker to have valid authentication credentials to the application. Once authenticated, the attacker can:

1. Navigate to the offer view functionality
2. Capture the request containing the offer_id parameter
3. Systematically modify the offer_id value to enumerate other users' offers
4. Access confidential quote information including client details, pricing, and business terms

The following code shows the security patch that addresses this vulnerability by implementing proper authorization checks:

 <?php
 include "db.php";
 
-if (!isset($_SESSION['user_id'])) { die("Yetkisiz erişim!"); }
+// 1️⃣ Authentication kontrolü
+if (!isset($_SESSION['user_id'])) {
+    http_response_code(401);
+    die("Yetkisiz erişim!");
+}
+
+$user_id = (int) $_SESSION['user_id'];
 
-$offer_id = isset($_GET['id']) ? (int)$_GET['id'] : 0;
-if ($offer_id <= 0) { die("Geçersiz Teklif ID'si"); }
+// 2️⃣ Güvenli offer_id okuma
+$offer_id = filter_input(INPUT_GET, 'id', FILTER_VALIDATE_INT);
+if (!$offer_id) {
+    http_response_code(400);
+    die("Geçersiz Teklif ID'si");
+}
 
-$offer_stmt = mysqli_prepare($conn, "SELECT o.*, u.email FROM offers o JOIN users u ON o.user_id = u.id WHERE o.id = ?");
+// 3️⃣ Teklif çek (SADECE ID ile)
+$offer_stmt = mysqli_prepare(
+    $conn,
+    "SELECT o.*, u.email 
+     FROM offers o 
+     JOIN users u ON o.user_id = u.id 
+     WHERE o.id = ?"
+);

Source: GitHub Commit Overview

Detection Methods for CVE-2026-23843

Indicators of Compromise

• Unusual patterns of sequential or incremental offer_id parameter values in HTTP requests from a single user session
• Multiple failed or successful access attempts to offers that don't belong to the requesting user
• Anomalous spikes in offer view requests from individual authenticated accounts
• Log entries showing access to a wide range of offer IDs that exceed normal user behavior patterns

Detection Strategies

• Implement application-level logging that captures the relationship between authenticated user IDs and requested offer IDs
• Deploy Web Application Firewall (WAF) rules to detect parameter tampering patterns indicative of IDOR enumeration
• Monitor for automated scanning behavior characterized by rapid sequential requests with incrementing ID values
• Enable database query logging to identify SELECT queries retrieving offers not associated with the requesting user

Monitoring Recommendations

• Configure alerts for users accessing more than a threshold number of unique offers within a short time window
• Implement real-time correlation between authentication logs and resource access logs
• Review access patterns periodically to identify accounts exhibiting enumeration behavior
• Integrate SentinelOne Singularity XDR for endpoint visibility and correlation of suspicious web application activity

How to Mitigate CVE-2026-23843

Immediate Actions Required

• Update teklifolustur_app to the patched version containing commit dd082a134a225b8dcd401b6224eead4fb183ea1c
• Review application logs for evidence of prior exploitation attempts
• Audit other endpoints in the application for similar IDOR vulnerabilities
• Implement input validation using filter_input() with appropriate validation filters

Patch Information

The vulnerability is resolved in commit dd082a134a225b8dcd401b6224eead4fb183ea1c. The patch adds proper authorization checks to ensure the authenticated user can only access their own offers. For detailed patch information, refer to the GitHub Security Advisory GHSA-6h9r-mmg3-cg7m.

Workarounds

• Implement a temporary middleware or application-level filter that validates resource ownership before processing requests
• Restrict access to the offer view functionality to specific trusted IP addresses or user roles until patching is complete
• Add manual authorization checks in the affected PHP files that compare $_SESSION['user_id'] against the offer's owner ID
• Consider deploying a reverse proxy with custom rules to enforce authorization at the network layer as an interim measure

# Example: Add authorization check to SQL query
# Modify your SQL WHERE clause to include user_id validation:
# "SELECT o.*, u.email FROM offers o JOIN users u ON o.user_id = u.id WHERE o.id = ? AND o.user_id = ?"
# Bind both offer_id and session user_id parameters