CVE-2026-21770: HCL Traveler for Microsoft Outlook DLL hijacking

CVE-2026-21770 · Severity: medium · CVSS 6.5 · Published 2026-07-17

HCL Traveler for Microsoft Outlook (HTMO), a tool that allows users to access HCL Domino mail and calendar data within the Outlook client, is vulnerable to a security flaw. An attacker with high-level access to a user's computer could replace legitimate application files with malicious ones. If successful, this could allow the attacker to take full control of the application, potentially leading to the theft of sensitive email data or further compromise of the local system.

Technologies: HCL Software Traveler for Microsoft Outlook. Vendors: HCL Software.

Quick answers

Is CVE-2026-21770 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-21770 being exploited in the wild.
How severe is CVE-2026-21770?
Medium severity, with a CVSS score of 6.5, published 17 July 2026.
Which products and versions are affected?
HCL Software Traveler for Microsoft Outlook < 3.0.16.
Is there a fix for CVE-2026-21770?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-21770 attacked?
It is attacked with local access, in a network appliance.
Am I affected by CVE-2026-21770?
Check whether you run HCL Software Traveler for Microsoft Outlook at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

HCL Traveler for Microsoft Outlook (HTMO) is vulnerable to DLL hijacking (CWE-427: Uncontrolled Search Path Element). The application fails to properly validate or restrict the search path used to load dynamic link libraries (DLLs), allowing an attacker to place a malicious DLL in a location where it will be loaded by the application. Exploitation requires local access and high privileges (PR:H) on the target machine, as well as user interaction (UI:R). Successful exploitation allows for arbitrary code execution with the privileges of the HTMO process, potentially compromising confidentiality, integrity, and availability. The vulnerability is addressed in HTMO version 3.0.16.

Affected products

  • HCL Software Traveler for Microsoft Outlook (HTMO) < 3.0.16

Timeline

  • 2026-07-17: disclosed
  • 2026-07-17: advisory

References

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