MobaXterm: Lack of integrity check allows DLL replacement by local attacker
Summary
MobaXterm Personal Edition (Portable) 26.4 GA extracts the CygUtils64.plugin file without verifying its integrity. A local attacker with write access to this plugin can replace the cygwin1.dll library with a malicious one. When the user opens a Local Shell session or uses a Cygwin-based function, the tampered library is loaded and code runs with the user's permissions, without privilege escalation.
Affected
- MobaXterm Personal Edition (Portable) 26.4 GA
- Home Edition: unknown, not confirmed by the sources reviewed
Fixed in
- MobaXterm 26.5 (released 11 September 2026, according to INCIBE) or later
Workaround
- Restrict write access to the MobaXterm portable folder and its plugin files to trusted accounts.
- Make CygUtils64.plugin and related binaries read-only.
- Compare existing installations against known-good file hashes.
Exploitation
- INCIBE lists exploitation as "No".
- VulDB states that no exploit is available.
- HOL reports that the CVE is not marked as known exploited.
- No public proof of concept found.
Our recommendation
- Inventory all MobaXterm installations, especially portable copies in user-writable locations such as Downloads or USB drives.
- Update all installations to MobaXterm 26.5 or later.
- Until patched, restrict write access to the MobaXterm folders.
- Verify the 26.5 release and contents on the Mobatek website, and check Home Edition separately.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- INCIBE-CERT advisory INCIBE-2026-758 www.incibe.es
- VulDB CVE-2026-112161 vuldb.com
- VulDB vulnerability 422289 vuldb.com
- OpenCVE CVE-2026-112161 app.opencve.io
- HOL Guard CVE-2026-112161 hol.org
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 10:26.
Original description (NVD)
MobaXterm Personal Edition (Portable) 26.4 GA extracts the CygUtils64.plugin file without first verifying its integrity. A local attacker with write permissions on this file can replace the ‘bin/cygwin1.dll’ library contained within it with a malicious library. When the victim opens a Local Shell session or uses a Cygwin-based function, the application extracts the component and loads the tampered library, executing code with the victim’s permissions. Exploitation requires write access to the plugin and does not, in itself, involve privilege escalation.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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