CVE-2026-27552: Authentication Bypass Vulnerability

CVE-2026-27552 Overview

CVE-2026-27552 is an improper authorization vulnerability [CWE-863] affecting the /index.php/attached_devices_tab/do_upload endpoint of an industrial device management interface. A low-privileged remote attacker can abuse the endpoint to upload IO-Device Description (IODD) files without proper authorization checks. The uploaded files can alter device behavior or trigger system crashes. CERT-VDE tracked the issue across advisories VDE-2026-014, VDE-2026-027, and VDE-2026-028. The flaw impacts integrity and availability of the affected devices while requiring only authenticated access at a low privilege level.

Critical Impact
An authenticated low-privileged attacker can remotely upload IODD files that modify device operation or crash the system, disrupting industrial processes.

Affected Products

Products referenced in CERT-VDE Advisory VDE-2026-014
Products referenced in CERT-VDE Advisory VDE-2026-027
Products referenced in CERT-VDE Advisory VDE-2026-028

Discovery Timeline

2026-09-16 - CVE CVE-2026-27552 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-27552

Vulnerability Analysis

The vulnerability resides in the do_upload action of the attached_devices_tab controller. This handler processes uploads of IODD files, which describe IO-Link devices and drive configuration logic on the target system. The endpoint fails to verify whether the authenticated caller holds the role required to modify device configuration. A low-privileged account can therefore submit an IODD file that the device accepts and processes as authoritative.

Once accepted, a malicious or malformed IODD file can steer the device toward incorrect operational states. Attackers can weaponize the primitive to change device behavior in industrial contexts or supply payloads that lead to a crash of the management service. The result is an integrity and availability compromise on network-reachable equipment.

Root Cause

The endpoint enforces authentication but omits authorization checks tied to the sensitive action of uploading device description files. Access control decisions are decoupled from the privileges required to change device configuration, matching the pattern described by CWE-863: Incorrect Authorization.

Attack Vector

Exploitation occurs over the network against the web management interface. The attacker authenticates with any valid low-privileged account, then issues a crafted HTTP POST request to /index.php/attached_devices_tab/do_upload carrying an IODD payload. No user interaction is required beyond the attacker's session, and no elevated role is needed to reach the vulnerable handler.

No verified public proof-of-concept is available. Refer to the CERT-VDE Advisory VDE-2026-014, CERT-VDE Advisory VDE-2026-027, and CERT-VDE Advisory VDE-2026-028 for vendor-specific technical detail.

Detection Methods for CVE-2026-27552

Indicators of Compromise

HTTP POST requests to /index.php/attached_devices_tab/do_upload originating from low-privileged user sessions.
Unexpected creation or modification of IODD files on the device file system.
Device restarts, service crashes, or configuration drift correlated with recent upload activity.

Detection Strategies

Correlate web access logs with authenticated user roles to flag privileged upload actions from non-privileged accounts.
Baseline normal IODD upload frequency and alert on deviations, including uploads outside change windows.
Inspect uploaded IODD file hashes against a known-good inventory maintained by operations staff.

Monitoring Recommendations

Forward device web server and application logs to a centralized SIEM for retention and search.
Monitor operational technology (OT) network segments for HTTP traffic to management endpoints from unusual source hosts.
Alert on repeated do_upload requests from the same session or IP within short intervals.

How to Mitigate CVE-2026-27552

Immediate Actions Required

Restrict network access to the device management interface to trusted administrative hosts only.
Audit user accounts and remove or downgrade any low-privileged accounts that are no longer required.
Review recent upload activity on /index.php/attached_devices_tab/do_upload for unauthorized IODD changes.

Patch Information

Apply the vendor updates referenced in CERT-VDE Advisory VDE-2026-014, CERT-VDE Advisory VDE-2026-027, and CERT-VDE Advisory VDE-2026-028. Consult each advisory for the specific affected versions and fixed releases that apply to your deployment.

Workarounds

Place the device behind a network firewall or VPN and block direct access from general user subnets.
Enforce role-based network segmentation so that only engineering workstations can reach management URLs.
Disable or lock accounts that do not require access to the web management interface until patches are deployed.