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Classic Buffer OverflowWeakness · CWE-120

CVE-2019-25741

CRITICAL · 9.8 CVSS v3.1 Published 2026-06-04
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Public exploit Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Buffer overflow vulnerability in MobaXterm 12.1 session file parsing where the username field lacks proper length validation, allowing overflow of a buffer and SEH (Structured Exception Handler) overwrite to achieve arbitrary code execution. Attackers distribute a crafted malicious .mxsc session file that when imported and executed by the victim triggers the overflow, enabling reverse shell execution with the user's privileges.

MitigationApply vendor patch for MobaXterm 12.1 if available; otherwise implement compensating controls such as application whitelisting, blocking session file imports from untrusted sources, and running MobaXterm with restricted privileges to limit impact of potential exploitation.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify MobaXterm installation and version
    Check for MobaXterm executable (typically at C:\Program Files (x86)\Mobatek\MobaXterm\MobaXterm.exe or C:\Program Files\Mobatek\MobaXterm\MobaXterm.exe). Right-click the executable, select Properties, and view the File version field. Alternatively, run MobaXterm and go to Help > About to see the version number.
    Affected if The installed version is 12.1 or falls within the affected version range containing this vulnerability.
  2. Locate session files on the system
    Search for .mxsession files in user directories. Common locations include: %USERPROFILE%\Documents\MobaXterm\sessions, %APPDATA%\Mobatek\MobaXterm\sessions, and the user's Documents folder. Use: dir /s /b *.mxsession 2>nul
    Affected if Any .mxsession files exist, particularly those from untrusted or unknown sources.
  3. Inspect session file structure for username field
    Open any .mxsession file in a hex editor or plain text editor (the file may be encoded). Look for the username field within the session configuration data. The vulnerability lies in the username field containing oversized data.
    Affected if A session file contains an abnormally long string in any username-related field, which could indicate attempted exploitation.
  4. Check for evidence of session file import activity
    Review recent file access timestamps on .mxsession files in the sessions folder. Check Windows Event Viewer for application logs around the time of any session file imports. Look for MobaXterm process creation events.
    Affected if Session files were recently imported, especially from removable media, downloads, or network shares.
  5. Monitor for anomalous MobaXterm process behavior
    Use Task Manager or Process Explorer to check running MobaXterm instances. Look for unexpected child processes, network connections initiated by MobaXterm (especially to external IPs), or unusual DLL injection.
    Affected if MobaXterm is running with unexpected network connections or spawning processes not typical of normal operation.

A user is affected if MobaXterm version 12.1 (or an affected version) is installed AND any untrusted or maliciously crafted .mxsession files have been imported into the application.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply vendor patch for MobaXterm 12.1 if available; otherwise implement compensating controls such as application whitelisting, blocking session file imports from untrusted sources, and running MobaXterm with restricted privileges to limit impact of potential exploitation.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2019-25741 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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