CVE-2026-13742: Honeywell IQ MultiAccess Signature Flaw

CVE-2026-13742 Overview

CVE-2026-13742 is an improper digital signature verification vulnerability affecting Honeywell IQ MultiAccess, all versions prior to and including version 28. The flaw allows an attacker to replace a downloaded file with a malicious one because signature validation is not correctly enforced. Exploitation requires local access with low privileges, and successful attacks can compromise the integrity and availability of the affected system. Honeywell has released fixed versions V27 SP1 and V28 SP1 to address the issue. The weakness is categorized under [CWE-367] (Time-of-check Time-of-use race condition).

Critical Impact
An attacker with local access can substitute a legitimate downloaded file with a malicious payload, undermining the integrity of the IQ MultiAccess installation and enabling downstream code execution or tampering.

Affected Products

Honeywell IQ MultiAccess, all versions up to and including V27
Honeywell IQ MultiAccess, all versions up to and including V28
Fixed in Honeywell IQ MultiAccess V27 SP1 and V28 SP1

Discovery Timeline

2026-06-29 - CVE CVE-2026-13742 published to NVD
2026-06-29 - Last updated in NVD database

Technical Details for CVE-2026-13742

Vulnerability Analysis

The vulnerability stems from improper digital signature verification in the IQ MultiAccess update or file download workflow. The product fails to reliably validate the signature on a downloaded file before consuming it. Because the underlying weakness is classified as [CWE-367], a time-of-check to time-of-use (TOCTOU) race condition exists between the moment the file is verified and the moment it is used. An attacker who can influence the file on disk in that window can substitute a malicious file that then executes with the trust of the original.

The attack vector is local, and the attacker must already hold low-level privileges on the host. No user interaction is required. Successful exploitation yields high impact on integrity and availability while confidentiality impact remains limited.

Root Cause

The root cause is a race condition in the signature verification routine. The application verifies the signature of a downloaded artifact and later opens or executes the file as a separate step. Between these two operations, the file can be swapped by a local attacker, causing the trusted verification result to be applied to attacker-controlled content.

Attack Vector

Exploitation requires local access to the system hosting IQ MultiAccess with authenticated low-privileged access. The attacker monitors the update or download workflow, waits for signature validation to complete, and then replaces the verified file before the application consumes it. The result is that unsigned or maliciously modified files are treated as authentic. See the Honeywell Product Security advisory portal for vendor-specific technical details.

// No verified public exploit code is available for CVE-2026-13742.
// The vulnerability mechanism involves a TOCTOU window between
// signature verification and file use. Refer to the Honeywell
// Product Security advisory for further technical detail.

Detection Methods for CVE-2026-13742

Indicators of Compromise

Unexpected modification timestamps on files staged for use by IQ MultiAccess between download and execution
Presence of unsigned or altered binaries in IQ MultiAccess installation or update directories
Local user accounts writing to IQ MultiAccess working directories outside of normal maintenance windows

Detection Strategies

Monitor file integrity for the IQ MultiAccess installation directory and any staging paths used for downloads and updates
Alert on writes to update staging locations from user accounts that are not the IQ MultiAccess service identity
Correlate signature-verification log events with subsequent file-open or execution events to identify anomalous gaps

Monitoring Recommendations

Enable process and file auditing on Windows hosts running IQ MultiAccess and forward events to a central SIEM
Track application update events and compare downloaded file hashes against vendor-published values from Honeywell Product Security
Watch for local privilege-use anomalies against accounts with access to the IQ MultiAccess directories

How to Mitigate CVE-2026-13742

Immediate Actions Required

Upgrade Honeywell IQ MultiAccess to V27 SP1 or V28 SP1 as recommended by the vendor
Restrict local logon rights to IQ MultiAccess hosts to essential administrators only
Apply strict file system permissions on IQ MultiAccess installation and update directories to prevent low-privileged writes

Patch Information

Honeywell recommends updating to the most recent version of the product: V27 SP1 or V28 SP1. Consult the Honeywell Product Security portal for release artifacts and installation guidance.

Workarounds

Limit interactive and remote local access to systems running IQ MultiAccess until the patch is applied
Manually verify the SHA-256 hash of any IQ MultiAccess download against vendor-published values before installation
Apply application allowlisting so only signed and approved binaries can execute on IQ MultiAccess hosts

bash

# Example: verify a downloaded installer hash before applying it
certutil -hashfile IQMultiAccess_V28SP1_installer.exe SHA256
# Compare the returned hash against the value published by Honeywell
# via https://www.honeywell.com/us/en/product-security before running.