National CERT Issues Urgent Update Warning For TeamViewer Users

National CERT urges TeamViewer users to update their software immediately following the discovery of a high-severity security flaw.

NationPulse Desk

Nov 1, 2026 · 7:50 PM 2 min read

Key takeaways

National CERT urged TeamViewer users to update the remote-access app due to a high-severity flaw.

The vulnerability, tracked as CVE-2026-111585, has a CVSS score of 8.8.

The flaw affects TeamViewer clients older than version 15.83 on Windows, macOS, and Linux.

The bug is an integer overflow in the part of TeamViewer that processes remote screen data.

Users should update to version 15.83 or later, or apply specific fixes for older branches.

National CERT strongly recommends that individuals and organizations running TeamViewer apply the latest software update to address a serious vulnerability that might permit malicious actors to execute unauthorized code or force application crashes.

Identified as CVE-2026-111585, the vulnerability carries a CVSS severity rating of 8.8. The security advisory points to TeamViewer security bulletins, noting the bug impacts clients running versions prior to 15.83 across Linux, macOS, and Windows systems.

How the Attack Works

The vulnerability stems from an integer overflow located within the component of TeamViewer responsible for handling remote screen data. Attackers controlling a malicious or compromised remote machine can transmit specific data payloads that trigger this flaw, leading to memory corruption or application failure.

Depending on the operating system, this issue might grant perpetrators the ability to execute code using the same permission level as the TeamViewer application itself. The exploit requires user interaction, meaning it only triggers when an individual establishes a connection to a device managed by the attacker.

Which Versions Are Affected

Impacted software includes the TeamViewer Full Client for Linux, macOS, and Windows, along with TeamViewer Portable for Windows and the Android Remote Control app. Users must upgrade to version 15.83 or newer. Separate patches exist for legacy branches, including version 14.7.48868 for the 14.x series and version 13.2.36231 for the 13.x series.

What Users Should Do

National CERT, following a prior warning issued to staff regarding a separate security threat, recommends that users and businesses implement the following measures:

Update all TeamViewer installations, including portable and older versions
Accept remote sessions only from verified, trusted people
Limit remote access to approved users and devices
Review unattended access and admin privileges
Watch for unexpected TeamViewer crashes or unusual sessions

If applying patches right away is not feasible, the advisory recommends blocking untrusted remote connections. Should a machine face potential compromise, organizations need to save log files, limit remote access, and contact incident response professionals.

Questions and answers

What is the CVE number and CVSS score for the TeamViewer flaw?

The flaw is tracked as CVE-2026-111585 and has a CVSS score of 8.8.

Which TeamViewer versions are affected?

It affects TeamViewer clients older than version 15.83 on Windows, macOS, and Linux, including TeamViewer Portable for Windows and the Android Remote Control app.

What should users do if they cannot patch immediately?

The advisory suggests blocking untrusted remote connections, preserving logs, restricting remote access, and seeking incident-response help if a device may be compromised.