Executive Summary

CVE-2026-11879 is a vulnerability in MobaXterm Personal Edition (Portable) version 26.3 (Build 5154) that allows arbitrary code execution. The issue arises because the application loads DLL files from a temporary directory that is predictable and can be modified by a local user. During startup, MobaXterm searches for specific DLLs in this temporary directory before checking the system's secure paths. An attacker with local access can place a specially crafted malicious DLL in this directory, which the application will then load and execute automatically when launched.

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Impact Analysis

This vulnerability can have a significant impact because it allows an attacker with local access to execute arbitrary code on the affected system. This means the attacker could potentially run malicious software with the privileges of the user running MobaXterm, leading to unauthorized actions such as data theft, system compromise, or further malware installation.

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Detection Guidance

This vulnerability involves loading malicious DLLs from a predictable temporary directory during the startup of MobaXterm Personal Edition (Portable) version 26.3 (Build 5154). Detection would require checking for the presence of unexpected or suspicious DLL files in the temporary directory used by the application.

Since the vulnerability requires local access and involves DLLs in a specific temporary directory, you can inspect that directory for unauthorized DLL files.

• On Windows, use commands like `dir %TEMP%\*.dll` in Command Prompt or `Get-ChildItem $env:TEMP\*.dll` in PowerShell to list DLL files in the temporary directory.
• Check the timestamps and origins of DLL files found there to identify any suspicious or recently added files that could be malicious.

Monitoring the startup behavior of MobaXterm for loading DLLs from the temporary directory can also help detect exploitation attempts.

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Mitigation Strategies

The immediate mitigation step is to update MobaXterm Personal Edition (Portable) from version 26.3 (Build 5154) to version 26.4 or later, where this vulnerability has been fixed by Mobatek.

Until the update can be applied, restrict local access to the system to trusted users only, as exploitation requires local access.

Additionally, monitor and restrict write permissions to the temporary directory used by MobaXterm to prevent unauthorized DLL placement.

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