CVE-2019-25741 in MobaXterm
Summary
by MITRE • 06/04/2026
Mobatek MobaXterm 12.1 contains a structured exception handling (SEH) based buffer overflow vulnerability in the username field of session files that allows remote attackers to execute arbitrary code. Attackers can craft a malicious MobaXterm sessions file with overflow data that triggers the vulnerability when imported and executed, enabling reverse shell execution with user privileges.
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Analysis
by VulDB Data Team • 06/04/2026
The vulnerability in Mobatek MobaXterm 12.1 represents a critical security flaw that exploits structured exception handling mechanisms within the application's session file processing functionality. This buffer overflow occurs specifically within the username field of session files, creating a pathway for remote attackers to gain unauthorized code execution privileges. The flaw demonstrates a classic software security weakness where insufficient input validation allows malicious data to overwrite adjacent memory regions, potentially leading to complete system compromise.
The technical implementation of this vulnerability stems from improper bounds checking during session file parsing operations. When MobaXterm processes a session file containing a specially crafted username field, the application fails to properly validate the input length before copying it into a fixed-size buffer. This oversight creates an exploitable condition where an attacker can overflow the buffer and overwrite the structured exception handler chain, ultimately redirecting program execution to malicious code. The vulnerability is classified as a classic stack-based buffer overflow, which falls under the CWE-121 category of buffer overflow conditions.
From an operational perspective, this vulnerability presents significant risk to users who may inadvertently import malicious session files from untrusted sources. The attack vector requires remote code execution capabilities through session file manipulation, making it particularly dangerous in environments where session files are shared across networks or downloaded from external sources. The successful exploitation enables attackers to establish reverse shell connections with the privileges of the user account running MobaXterm, potentially providing access to sensitive data and system resources. This vulnerability directly aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as it allows for arbitrary command execution within the target environment.
The impact of this vulnerability extends beyond simple code execution, as it can facilitate further exploitation attempts including privilege escalation and lateral movement within network environments. Security professionals should consider implementing network segmentation and access controls to limit the potential damage from such exploits. Organizations utilizing MobaXterm should prioritize immediate patching and implementation of session file validation policies to prevent unauthorized imports. The vulnerability demonstrates the importance of robust input validation and proper exception handling in client-side applications, particularly those handling external data inputs. Mitigation strategies should include regular security updates, user education regarding file import risks, and implementation of network monitoring to detect suspicious session file activities.