CVE-2021-27860

What is this vulnerability?

CVE-2021-27860 is categorized as a critical Unrestricted File Upload flaw with a CVSS base score of 9.8. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.

A vulnerability in the web management interface of FatPipe WARP, IPVPN, and MPVPN software prior to versions 10.1.2r60p92 and 10.2.2r44p1 allows a remote, unauthenticated attacker to upload a file to any location on the filesystem. The FatPipe advisory identifier for this vulnerability is FPSA006.

This architectural defect enables adversaries to bypass intended security controls, directly manipulating the application's execution state or data layer. Immediate strategic intervention is required.

Risk Assessment

Impact on Systems

✅ Data Exfiltration: Attackers can extract sensitive data from backend databases, configuration files, or internal services.

✅ Authentication Bypass: Exploiting this flaw may allow unauthorized access to protected resources and administrative interfaces.

✅ Lateral Movement: Once initial access is gained, attackers can pivot to internal systems and escalate privileges.

How to Fix and Mitigate CVE-2021-27860

1. Apply Vendor Patches Immediately: This vulnerability is listed in CISA's Known Exploited Vulnerabilities catalog. Apply updates per vendor instructions.
2. Verify Patch Deployment: Confirm all instances are updated using Precogs continuous monitoring.
3. Review Audit Logs: Investigate historical access logs for indicators of compromise related to this attack surface.
4. Implement Defense-in-Depth: Deploy WAF rules, network segmentation, and endpoint detection to limit blast radius.

Defending with Precogs AI

The FatPipe WARP web management interface fails to validate uploaded files. Attackers upload a malicious payload to an unrestricted directory to achieve remote code execution. Precogs Application Security Module maps untrusted file uploads directly to executable web roots.

Use Precogs to continuously scan your codebase, binaries, APIs, and infrastructure for this vulnerability class and related attack patterns. Our AI-powered detection engine combines static analysis with threat intelligence to identify exploitable weaknesses before attackers do.

Start scanning with Precogs →

Vulnerability Code Signature

Attack Data Flow

Vulnerable Code Pattern

// ❌ VULNERABLE: Unrestricted Upload
$target_dir = "uploads/";
$target_file = $target_dir . basename($_FILES["fileToUpload"]["name"]);
// Taint sink: saving file without extension/type validation
move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_file);

Secure Code Pattern

// ✅ SECURE: Validated Upload
$target_dir = "uploads/";
$filename = basename($_FILES["fileToUpload"]["name"]);
$filetype = strtolower(pathinfo($filename, PATHINFO_EXTENSION));

// Sanitized validation: strict allowlist
$allowed_types = array("jpg", "png", "gif");
if (in_array($filetype, $allowed_types)) {
    // Generate safe unique filename
    $safe_filename = uniqid() . "." . $filetype;
    move_uploaded_file($_FILES["fileToUpload"]["tmp_name"], $target_dir . $safe_filename);
}

How Precogs Detects This

Precogs AI Analysis Engine utilizes semantic taint tracking to detect insecure file upload routines and missing extension validation.\n