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CVE-2021-25265

8.8 HIGH
Remote Code Execution

📋 TL;DR

CVE-2021-25265 is a remote code execution vulnerability in Sophos Connect Client where a malicious website could execute arbitrary code on affected systems. This affects users running Sophos Connect Client versions before 2.1 on Windows systems. The vulnerability allows attackers to compromise client systems through web-based attacks.

💻 Affected Systems

Products:
  • Sophos Connect Client
Versions: All versions before 2.1
Operating Systems: Windows
Default Config Vulnerable: ⚠️ Yes
Notes: Only affects Windows versions of Sophos Connect Client. The vulnerability is in the client software itself, not dependent on specific configurations.

📦 What is this software?

Connect by Sophos

View all CVEs affecting Connect →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete system compromise allowing attackers to install malware, steal credentials, pivot to internal networks, and maintain persistent access.

🟠

Likely Case

Malware installation leading to data theft, ransomware deployment, or credential harvesting from the compromised system.

🟢

If Mitigated

Limited impact with proper network segmentation, application whitelisting, and endpoint protection preventing successful exploitation.

🌐 Internet-Facing: HIGH - Exploitation requires visiting a malicious website, which is common for client systems with internet access.
🏢 Internal Only: MEDIUM - Risk exists if users visit compromised internal websites or if attackers pivot from other compromised systems.

🎯 Exploit Status

Public PoC: ✅ No
Weaponized: LIKELY
Unauthenticated Exploit: ⚠️ Yes
Complexity: LOW

Exploitation requires user interaction (visiting malicious website) but no authentication. The CVSS score of 8.8 indicates relatively straightforward exploitation.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 2.1 and later

Vendor Advisory: https://community.sophos.com/b/security-blog/posts/resolved-rce-in-sophos-connect-client-for-windows-cve-2021-25265

Restart Required: Yes

Instructions:

1. Download Sophos Connect Client version 2.1 or later from Sophos website. 2. Uninstall previous version. 3. Install new version. 4. Restart system.

🔧 Temporary Workarounds

Disable Sophos Connect Client

windows

Temporarily disable or uninstall Sophos Connect Client until patching is possible.

Control Panel > Programs > Uninstall a program > Select Sophos Connect Client > Uninstall

Web Browser Restrictions

all

Implement web filtering to block potentially malicious websites and restrict browser execution capabilities.

🧯 If You Can't Patch

  • Implement application whitelisting to prevent execution of unauthorized code
  • Deploy network segmentation to limit lateral movement if exploitation occurs

🔍 How to Verify

Check if Vulnerable:

Check Sophos Connect Client version in Control Panel > Programs > Programs and Features. If version is below 2.1, system is vulnerable.

Check Version:

wmic product where name="Sophos Connect Client" get version

Verify Fix Applied:

Verify Sophos Connect Client version is 2.1 or higher after installation.

📡 Detection & Monitoring

Log Indicators:

  • Unexpected process execution from Sophos Connect Client
  • Network connections from Sophos Connect to unusual destinations
  • Windows Event Log entries showing Sophos Connect crashes or unexpected behavior

Network Indicators:

  • Outbound connections from Sophos Connect Client to unknown IP addresses
  • Unusual web traffic patterns from systems running Sophos Connect

SIEM Query:

source="windows" AND (process_name="*sophos*" OR process_name="*connect*") AND (event_id=4688 OR event_id=1) AND (command_line="*powershell*" OR command_line="*cmd*")

📊 Metadata

CVE ID: CVE-2021-25265
CVSS v3 Score: 8.8 (HIGH)
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Published: March 22, 2021
Last Updated: November 21, 2024

🔗 References

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