CVE-2026-19377
Deferred Deferred - Pending Action

Improper Certificate Validation in Cato Client Tunnel Handshake

Publication date: 2026-10-15

Last updated on: 2026-10-15

Assigner: Cato

Description
Improper certificate validation in the tunnel handshake in Cato Client allows a man-in-the-middle attacker to impersonate a Cato Point of Presence (PoP) server and intercept or modify tunnel traffic.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-10-15
Last Modified
2026-10-15
Generated
2026-10-19
AI Q&A
2026-10-15
EPSS Evaluated
2026-10-18
NVD
CVE-2026-19377
EUVD
EUVD-2026-101881

Affected Vendors & Products

Showing 5 associated CPEs
Vendor Product Version / Range
Cato Networks Cato Client for Windows 0
Cato Networks Cato Client for macOS 0
Cato Networks Cato Client for Linux 0
Cato Networks Cato Client for iOS 0
Cato Networks Cato Client for Android 0

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-295 The product does not validate, or incorrectly validates, a certificate.

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

This vulnerability involves improper certificate validation during the tunnel handshake in Cato Client. A man-in-the-middle attacker can exploit this to impersonate a Cato Point of Presence server, intercepting or modifying tunnel traffic between the client and server.

Detection Guidance

Detect vulnerable Cato Client versions by checking installed software versions against patched releases. Use the Access Overview Dashboard in the Cato Management Application to identify outdated clients. For manual checks, compare installed versions against: Windows v6.12.6, macOS v6.1.1, Linux v5.8.1, iOS v5.9, Android v5.6.2.

Impact Analysis

If exploited, this vulnerability allows attackers to intercept sensitive data transmitted through the tunnel, such as login credentials or confidential information. It could also enable attackers to modify data in transit, leading to potential data breaches or unauthorized access to systems.

Compliance Impact

This vulnerability could undermine compliance with GDPR and HIPAA by enabling man-in-the-middle attacks that intercept or modify sensitive data transmitted through the Cato Client tunnel. Improper certificate validation risks unauthorized access to personal or protected health information, violating confidentiality requirements under these regulations.

Mitigation Strategies

Immediately upgrade all Cato Client installations to the minimum patched versions: Windows v6.12.6, macOS v6.1.1, Linux v5.8.1, iOS v5.9, Android v5.6.2. Use the Client Rollout page in CMA for Windows, macOS, and Linux, or update via App Store/Google Play for mobile. Enable automatic updates through the Cato upgrade service.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-19377. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart