CVE-2025-5261: Pik Online Auth Bypass Vulnerability

CVE-2025-5261 Overview

CVE-2025-5261 is an Authorization Bypass Through User-Controlled Key vulnerability (CWE-639) affecting Pik Online software developed by Pik Online Yazılım Çözümleri A.Ş. This vulnerability enables attackers to exploit trusted identifiers, potentially gaining unauthorized access to sensitive information through insecure direct object references. The flaw allows malicious actors to manipulate user-controlled keys to bypass authorization controls without requiring authentication.

Critical Impact

Unauthorized access to confidential data through exploitation of trusted identifiers, potentially exposing sensitive business or user information in affected Pik Online deployments.

Affected Products

• Pik Online versions before 3.1.5

Discovery Timeline

• 2025-08-20 - CVE CVE-2025-5261 published to NVD
• 2025-08-20 - Last updated in NVD database

Technical Details for CVE-2025-5261

Vulnerability Analysis

This vulnerability falls under CWE-639 (Authorization Bypass Through User-Controlled Key), also known as Insecure Direct Object Reference (IDOR). The application fails to properly validate whether the authenticated user has permission to access the resource identified by a user-supplied key or identifier. This allows attackers to access or modify data belonging to other users by simply changing the identifier value in requests.

The network-based attack vector requires no user interaction and can be exploited without prior authentication. The primary impact is on confidentiality, as attackers can potentially access sensitive data they are not authorized to view. The vulnerability affects Pik Online versions prior to 3.1.5.

Root Cause

The root cause of this vulnerability lies in improper authorization validation within the Pik Online application. When processing requests that include user-controlled identifiers (such as user IDs, document IDs, or other resource references), the application fails to verify that the requesting user has legitimate access rights to the specified resource. Instead of performing proper authorization checks, the application trusts the identifier supplied by the user, assuming that possession of the identifier implies authorization to access the associated resource.

Attack Vector

The attack vector is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by:

1. Intercepting legitimate requests to identify the parameter structure used for resource identification
2. Manipulating the user-controlled key values (such as incrementing numeric IDs or substituting known identifiers)
3. Sending modified requests to access resources belonging to other users or entities
4. Extracting sensitive information from unauthorized resources

The vulnerability is exploitable remotely without authentication, making it particularly dangerous for internet-facing deployments. For detailed technical information, refer to the USOM Security Notification TR-25-0201.

Detection Methods for CVE-2025-5261

Indicators of Compromise

• Unusual patterns of sequential or enumerated resource access attempts from single sources
• Access logs showing users retrieving resources they don't own or shouldn't have access to
• Anomalous API request patterns with systematically modified identifier parameters
• Increased volume of requests to sensitive resource endpoints with varying ID parameters

Detection Strategies

• Implement web application firewall (WAF) rules to detect sequential identifier enumeration patterns
• Deploy behavioral analytics to identify users accessing abnormal quantities of distinct resources
• Configure intrusion detection systems to alert on suspicious parameter manipulation in HTTP requests
• Review application logs for access attempts to resources outside user authorization boundaries

Monitoring Recommendations

• Enable detailed logging for all resource access operations including user identity and accessed resource identifiers
• Monitor for failed authorization attempts that may indicate exploitation attempts
• Establish baseline patterns for normal resource access and alert on deviations
• Implement rate limiting on sensitive endpoints to slow enumeration attacks

How to Mitigate CVE-2025-5261

Immediate Actions Required

• Upgrade Pik Online to version 3.1.5 or later immediately
• Audit access logs to identify potential exploitation attempts or unauthorized data access
• Implement additional authorization controls at the network level while patching is in progress
• Review and validate all user-accessible resource endpoints for proper authorization checks

Patch Information

Pik Online Yazılım Çözümleri A.Ş. has addressed this vulnerability in Pik Online version 3.1.5. Organizations running affected versions should upgrade immediately to the patched version. Additional technical details and patch information are available in the USOM Security Notification TR-25-0201.

Workarounds

• Deploy a web application firewall (WAF) with rules to detect and block IDOR exploitation attempts
• Implement additional server-side authorization validation at the reverse proxy or API gateway level
• Restrict access to sensitive endpoints to authenticated users from trusted IP ranges where feasible
• Consider implementing indirect reference maps to obfuscate direct object identifiers until patching is complete

# Example: Configure rate limiting for sensitive endpoints (nginx)
# Add to server block to limit enumeration attempts
limit_req_zone $binary_remote_addr zone=resource_limit:10m rate=10r/s;

location /api/resources/ {
    limit_req zone=resource_limit burst=20 nodelay;
    # Additional authorization controls
}