CVE-2026-16444: TeamViewer Desktop Path Traversal Flaw

CVE-2026-16444 Overview

CVE-2026-16444 is a path traversal vulnerability affecting TeamViewer Desktop Clients prior to version 15.81.5. The flaw stems from improper neutralization of path traversal sequences in the file transfer and virtual file clipboard mechanisms. An authenticated remote session participant can write files to unintended locations on the local file system. Attackers can leverage this behavior to achieve arbitrary file write and potentially execute code with the privileges of the affected user. The vulnerability is classified under [CWE-73] External Control of File Name or Path.

Critical Impact
Authenticated session participants can write arbitrary files to unintended filesystem locations, enabling potential code execution as the local user.

Affected Products

TeamViewer Desktop Client for Windows prior to version 15.81.5
TeamViewer Desktop Client for macOS prior to version 15.81.5
TeamViewer Desktop Client for Linux prior to version 15.81.5

Discovery Timeline

2026-08-26 - CVE CVE-2026-16444 published to NVD
2026-08-27 - Last updated in NVD database

Technical Details for CVE-2026-16444

Vulnerability Analysis

The vulnerability resides in how TeamViewer Desktop Clients handle file names during remote session file operations. The client fails to properly neutralize path traversal sequences such as ../ or absolute path references when receiving files from a remote session participant. This affects both the standard file transfer feature and the virtual file clipboard mechanism used to copy files between session endpoints.

When a remote participant sends a file with a crafted name, the receiving client writes the file to an attacker-controlled path rather than the intended download directory. An attacker who plants an executable, shortcut, or configuration file in a sensitive location can achieve code execution with the privileges of the user running TeamViewer.

Root Cause

The root cause is insufficient input validation on file path components received during session file operations. The client accepts path separators and traversal sequences embedded in file names without canonicalizing the resulting path or enforcing that the destination remains within the intended directory boundary.

Attack Vector

Exploitation requires an active remote session and user interaction to accept or trigger file transfer. The attacker must be an authenticated session participant. Once in a session, the attacker submits a file whose name contains traversal sequences pointing to a sensitive filesystem location such as a user startup folder or an autorun path. The receiving client writes the file at the attacker-specified location without warning.

The vulnerability manifests in the file transfer and virtual clipboard code paths. See the TeamViewer Security Bulletin TV-2026-1008 for vendor-supplied technical details.

Detection Methods for CVE-2026-16444

Indicators of Compromise

Files written outside of the configured TeamViewer download directory, particularly in user startup folders, Windows %APPDATA% paths, or ~/.config autorun locations
TeamViewer log entries referencing file names containing ../, ..\, or absolute path prefixes
Unexpected executables or shortcuts appearing on hosts shortly after a TeamViewer session

Detection Strategies

Monitor TeamViewer client log files for file transfer events where the destination path deviates from the configured incoming file directory
Alert on file creation events in autorun-relevant directories where the parent process is a TeamViewer binary
Correlate remote session connection events with subsequent filesystem writes to sensitive user or system paths

Monitoring Recommendations

Enable verbose logging on TeamViewer clients and forward logs to a centralized SIEM for retention and analysis
Track TeamViewer client versions across the endpoint inventory to identify hosts still running builds prior to 15.81.5
Baseline normal file transfer destinations for TeamViewer users and alert on deviations

How to Mitigate CVE-2026-16444

Immediate Actions Required

Upgrade all TeamViewer Desktop Clients to version 15.81.5 or later across Windows, macOS, and Linux endpoints
Restrict inbound TeamViewer sessions to trusted, authenticated participants and enforce session approval prompts
Audit recent TeamViewer file transfer activity for evidence of exploitation on hosts that ran vulnerable builds

Patch Information

TeamViewer has released version 15.81.5 which corrects the improper neutralization of path traversal sequences in file transfer and virtual file clipboard handling. Refer to the TeamViewer Security Bulletin TV-2026-1008 for the authoritative patched version list and update instructions.

Workarounds

Disable the file transfer feature in TeamViewer client policy where operationally feasible until the patch is deployed
Disable the virtual file clipboard feature to eliminate the secondary exploitation path
Limit TeamViewer usage to accounts with least privilege to reduce the impact of arbitrary file write as the current user

bash

# Configuration example
# Verify installed TeamViewer version on Windows
reg query "HKLM\SOFTWARE\TeamViewer" /v Version

# Verify installed TeamViewer version on Linux
teamviewer --version