CVE-2026-1078

Executive Summary

CVE-2026-1078 is an arbitrary file-write vulnerability discovered in the Pega Browser Extension (PBE), specifically affecting Pega Robotic Automation versions 22.1 or R25. The flaw allows a remote attacker to write arbitrary files to the victim's filesystem by luring a Robot Runtime user to a malicious website. This is a client-side attack vector that requires user interaction (navigating to a malicious site) and leverages the trust relationship between the browser extension and the local file system. No public proof-of-concept (PoC) or exploit code has been released, and the vendor has not yet issued a patch. The vulnerability is classified under CWE-22 (Path Traversal) and aligns with MITRE ATT&CK tactic T1204 (User Execution).

Supply Chain & Package Security

This vulnerability is not related to an open-source package manager (NPM, PyPI, Go, Ruby). It affects a proprietary enterprise automation product (Pega Robotic Automation) and its browser extension. Supply chain risk is limited to the distribution channel of the Pega Browser Extension itself.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, indicating that no official CVSS vector has been assigned by NVD at this time. However, based on the description, a reasonable assessment would be:

• Attack Vector (AV): Network (malicious website)
• Attack Complexity (AC): Low (no special conditions)
• Privileges Required (PR): None (attacker does not need prior access)
• User Interaction (UI): Required (victim must navigate to the site)
• Scope (S): Changed (vulnerability in extension impacts the host system)
• Confidentiality (C): None (file write, not read)
• Integrity (I): High (arbitrary file write can overwrite critical files)
• Availability (A): High (could overwrite system files causing denial of service)

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:H Estimated Score: 8.2 (High)

Deep Dive & Mechanics

The vulnerability resides in the Pega Browser Extension (PBE), which is used by Pega Robotic Automation to interact with web browsers (Chrome/Edge) during automation runs. The extension likely exposes a native messaging host or a file system API that allows writing files to the local machine. The flaw occurs when the extension does not properly validate or sanitize file paths provided by external content (e.g., from a malicious website). An attacker can craft a website that, when visited by a Robot Runtime user, triggers the extension to write a file to an arbitrary location, such as:

• Overwriting system executables (e.g., C:\Windows\System32\drivers\etc\hosts)
• Dropping a malicious script into startup folders
• Modifying configuration files for persistence

The attack flow:

1. Victim (Robot Runtime user) navigates to attacker-controlled website.
2. Website contains JavaScript that communicates with the Pega Browser Extension via chrome.runtime.sendMessage or similar API.
3. Extension receives a crafted message containing a file path and content.
4. Extension writes the content to the specified path without proper validation (path traversal or lack of allowlist).
5. Attacker achieves arbitrary file write on the victim's system.

Vulnerable vs. Patched Code

Since no patch is available, we can only hypothesize the vulnerable code pattern. The extension likely has a function similar to:

// Vulnerable code (hypothetical)
chrome.runtime.onMessageExternal.addListener(
  function(request, sender, sendResponse) {
    if (request.action === "writeFile") {
      // No path validation
      fs.writeFileSync(request.path, request.content);
    }
  }
);

A patched version would include:

// Patched code (hypothetical)
const ALLOWED_DIR = path.join(process.env.APPDATA, "Pega", "Automation");
chrome.runtime.onMessageExternal.addListener(
  function(request, sender, sendResponse) {
    if (request.action === "writeFile") {
      const resolvedPath = path.resolve(request.path);
      // Ensure the resolved path is within the allowed directory
      if (!resolvedPath.startsWith(ALLOWED_DIR)) {
        sendResponse({error: "Access denied"});
        return;
      }
      fs.writeFileSync(resolvedPath, request.content);
    }
  }
);

Exploitation & Lab Setup

Red Team

Lab Setup:

• Windows 10/11 VM with Pega Robotic Automation 22.1 installed and Chrome/Edge.
• Attacker machine with a simple HTTP server hosting malicious HTML.

Exploitation Steps:

1. Create a malicious HTML page that sends a crafted message to the Pega Browser Extension.
2. Host the page on a local or public web server.
3. Lure the victim (Robot Runtime user) to visit the page.
4. The extension writes a malicious executable to the startup folder (e.g., C:\Users\<user>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\malware.exe).
5. On next login, the malware executes.

Example Malicious HTML (conceptual):

<!DOCTYPE html>
<html>
<body>
<script>
// This is a conceptual example; actual API may differ
chrome.runtime.sendMessage(
  "extension-id-here",
  {
    action: "writeFile",
    path: "C:\\Users\\victim\\AppData\\Roaming\\Microsoft\\Windows\\Start Menu\\Programs\\Startup\\evil.exe",
    content: "base64-encoded-binary"
  },
  function(response) {
    console.log(response);
  }
);
</script>
</body>
</html>

Blue Team

Detection Steps:

• Monitor for unusual file writes by the Pega Browser Extension process (e.g., chrome.exe or msedge.exe spawning child processes or writing to sensitive directories).
• Enable Windows Event Logging for file creation events (Event ID 4663) and correlate with the extension's process ID.
• Use Sysmon to log file creation events (Event ID 11) and network connections (Event ID 3) from the browser process.

Hunting Query (KQL):

DeviceFileEvents
| where FileName endswith ".exe" or FileName endswith ".dll" or FileName endswith ".ps1"
| where InitiatingProcessFileName in~ ("chrome.exe", "msedge.exe")
| where FolderPath startswith "C:\\Users" and FolderPath contains "Startup"
| project Timestamp, DeviceName, InitiatingProcessFileName, FolderPath, FileName

Indicators of Compromise (IOCs)

• File Paths: C:\Users\<username>\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\*.exe
• Process Names: chrome.exe, msedge.exe (with Pega extension loaded)
• Network: Connections to attacker-controlled domains hosting malicious JavaScript
• Registry: HKCU\Software\Microsoft\Windows\CurrentVersion\Run (if persistence via registry)
• Extension ID: The specific Pega Browser Extension ID (varies by version)

Detection Engineering

YARA Rule

rule CVE_2026_1078_Pega_File_Write {
    meta:
        description = "Detects potential exploitation of CVE-2026-1078 via Pega Browser Extension"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2026-1078"
    strings:
        $s1 = "writeFile" ascii wide nocase
        $s2 = "Pega" ascii wide nocase
        $s3 = "Robotic" ascii wide nocase
        $s4 = "Startup" ascii wide nocase
    condition:
        all of ($s1, $s2, $s3) or ($s1 and $s4)
}

Sigma Rule

title: CVE-2026-1078 - Pega Browser Extension Arbitrary File Write
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects file writes to startup folders by browser processes (Chrome/Edge) indicative of CVE-2026-1078 exploitation
author: Valters IT
date: 2025-04-10
logsource:
    category: file_event
    product: windows
detection:
    selection:
        Image|endswith:
            - '\chrome.exe'
            - '\msedge.exe'
        TargetFilename|contains:
            - '\Start Menu\Programs\Startup\'
            - '\AppData\Roaming\Microsoft\Windows\Start Menu\'
    condition: selection
falsepositives:
    - Legitimate automation tasks writing to startup folders (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-1078 - Pega Browser Extension Potential Exploit"; flow:to_server,established; content:"writeFile"; http_client_body; nocase; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the Pega Browser Extension on all systems running Pega Robotic Automation 22.1 or R25 until a patch is released.
2. Restrict browser extension permissions via Group Policy to prevent the extension from accessing file system APIs.
3. Educate users (especially Robot Runtime operators) not to browse untrusted websites while automations are running.

Long-term Fix:

• Apply vendor patch when available (monitor Pega support portal).
• Implement application whitelisting to prevent unauthorized executables from running in startup folders.
• Use endpoint detection and response (EDR) tools to monitor for suspicious file writes by browser processes.

Workaround:

• Configure the browser to run in a sandboxed environment (e.g., using Windows Sandbox or a dedicated VM) for automation tasks.

Valters IT

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