CVE-2020-37095: Cyberoam Client Buffer Overflow Flaw

CVE-2020-37095 Overview

CVE-2020-37095 is a buffer overflow vulnerability affecting Cyberoam Authentication Client version 2.1.2.7. This security flaw allows remote attackers to execute arbitrary code by exploiting a Structured Exception Handler (SEH) memory overwrite condition. The vulnerability is triggered through maliciously crafted input in the 'Cyberoam Server Address' field, which can lead to a bind TCP shell on port 1337 with system-level access.

Critical Impact

Successful exploitation of this buffer overflow vulnerability enables attackers to gain system-level code execution through SEH overwrite, potentially compromising the entire host system.

Affected Products

• Cyberoam Authentication Client version 2.1.2.7

Discovery Timeline

• 2026-02-07 - CVE-2020-37095 published to NVD
• 2026-02-09 - Last updated in NVD database

Technical Details for CVE-2020-37095

Vulnerability Analysis

This vulnerability is classified as CWE-121 (Stack-based Buffer Overflow), a memory corruption flaw that occurs when a program writes more data to a buffer on the stack than it was allocated to hold. In the case of Cyberoam Authentication Client, the application fails to properly validate the length of user-supplied input in the 'Cyberoam Server Address' field before copying it to a fixed-size stack buffer.

The exploitation technique leverages Structured Exception Handler (SEH) overwrite, a classic Windows exploitation method. When the buffer overflow occurs, it corrupts the SEH chain stored on the stack. By carefully crafting the overflow payload, an attacker can redirect program execution to attacker-controlled code when an exception is triggered.

The attack requires local access to the system where the vulnerable client is installed, and some user interaction is necessary to trigger the vulnerability. However, once exploited, the attacker gains system-level privileges, making this a significant security concern for organizations using this authentication client.

Root Cause

The root cause of CVE-2020-37095 is improper input validation in the Cyberoam Authentication Client's handling of the 'Cyberoam Server Address' field. The application allocates a fixed-size buffer for storing the server address but does not verify that user input fits within this buffer before performing a copy operation. This lack of bounds checking allows an attacker to provide an oversized input string that overwrites adjacent memory, including the Structured Exception Handler records on the stack.

Attack Vector

The attack vector for this vulnerability requires local access to a system running the vulnerable Cyberoam Authentication Client. The attacker must be able to interact with the application's user interface, specifically the 'Cyberoam Server Address' input field.

The exploitation process involves:

1. Crafting a malicious payload containing shellcode and SEH overwrite addresses
2. Entering the payload into the 'Cyberoam Server Address' field
3. The oversized input overflows the stack buffer and corrupts the SEH chain
4. When an exception occurs, the corrupted SEH handler redirects execution to the attacker's shellcode
5. The shellcode establishes a bind TCP shell on port 1337 with system privileges

Technical details and proof-of-concept information can be found in the Exploit-DB #48148 entry and the VulnCheck Advisory.

Detection Methods for CVE-2020-37095

Indicators of Compromise

• Unexpected TCP connections or listeners on port 1337 from the Cyberoam Authentication Client process
• Anomalous memory access patterns or application crashes in Cyberoam Authentication Client
• System logs indicating SEH exceptions or access violations in the client application
• Presence of shellcode patterns in memory dumps of the affected process

Detection Strategies

• Monitor for abnormal network activity originating from CyberoamClient.exe, particularly outbound or listening connections on unusual ports such as 1337
• Implement endpoint detection rules to identify buffer overflow exploitation attempts targeting SEH chains
• Deploy memory protection technologies such as DEP and ASLR enforcement to detect and prevent SEH-based exploits
• Configure application whitelisting to prevent unauthorized code execution from compromised processes

Monitoring Recommendations

• Enable Windows Event Logging for application crashes and exceptions, monitoring for patterns indicative of exploitation attempts
• Implement network traffic analysis to detect bind shells or reverse shell connections on non-standard ports
• Deploy SentinelOne Singularity to provide real-time behavioral detection of memory corruption exploits and unauthorized process injection
• Regularly audit systems for the presence of vulnerable Cyberoam Authentication Client version 2.1.2.7

How to Mitigate CVE-2020-37095

Immediate Actions Required

• Identify and inventory all systems running Cyberoam Authentication Client version 2.1.2.7
• Consider uninstalling or disabling the vulnerable application until a patched version is available
• Restrict local access to systems running the vulnerable client to authorized users only
• Implement network segmentation to limit potential lateral movement if exploitation occurs
• Deploy endpoint protection solutions capable of detecting buffer overflow and SEH exploitation attempts

Patch Information

Users should check for updated versions of Cyberoam Authentication Client. For product information and potential updates, refer to the Cyberoam Authentication Client Info page. As the Cyberoam product line has been integrated into Sophos, organizations should also consult Sophos security advisories for guidance on successor products or migration paths.

Workarounds

• Restrict access to the Cyberoam Authentication Client application to only trusted users
• Implement application-level firewalls to block unexpected network connections from the client process
• Enable Windows exploit protection features including DEP, ASLR, and SEHOP to mitigate SEH-based attacks
• Monitor systems for signs of compromise and isolate affected machines immediately if exploitation is suspected

# Windows Defender Exploit Protection - Enable SEH Overwrite Protection (SEHOP)
# Run in PowerShell as Administrator
Set-ProcessMitigation -Name "CyberoamClient.exe" -Enable SEHOP,DEP,ForceRelocateImages