CVE-2026-55728: Loytec LINX Buffer Overflow Vulnerability

CVE-2026-55728 Overview

CVE-2026-55728 is a stack-based buffer overflow [CWE-121] in the /usr/bin/ltsudo binary shipped with multiple Loytec building-automation devices. The flaw resides in the cmd_ipaddr_conflict handler and is triggered by supplying an overly long interface-name argument. Because ltsudo runs as a SUID-root process, a local attacker in the superadmin group can abort the process or potentially elevate privileges to root. Affected devices include Loytec LIP-ME201C, L-INX, L-GATE, L-ROC, L-IOB, L-DALI, L-VIS, and L-PAD through version 8.4.16 on the LINX-A64 platform.

Critical Impact
A local superadmin user can corrupt the stack of a SUID-root process, leading to process abort or possible privilege escalation to root on affected Loytec LINX-A64 devices.

Affected Products

Loytec LIP-ME201C, L-INX, L-GATE, L-ROC through firmware 8.4.16 on LINX-A64
Loytec L-IOB, L-DALI through firmware 8.4.16 on LINX-A64
Loytec L-VIS and L-PAD through firmware 8.4.16 on LINX-A64

Discovery Timeline

2026-07-24 - CVE-2026-55728 published to NVD
2026-07-27 - Last updated in NVD database

Technical Details for CVE-2026-55728

Vulnerability Analysis

The vulnerability is a classic stack-based buffer overflow inside the cmd_ipaddr_conflict subcommand of /usr/bin/ltsudo. ltsudo is a SUID-root helper used to execute a restricted set of privileged commands on Loytec LINX-A64 firmware. When a caller invokes the cmd_ipaddr_conflict code path and supplies an interface-name argument, the argument is copied into a fixed-size stack buffer without adequate length validation. Supplying an interface name that exceeds the buffer size overwrites adjacent stack data, including saved registers and the return address.

Exploitation requires local access and membership in the superadmin group, so the attacker must already hold elevated administrative privileges on the device. The immediate observable effect is a process abort, but the corruption of a SUID-root process stack creates the conditions for privilege escalation from superadmin to root, depending on the compiler-level protections active in the shipped binary.

Root Cause

The root cause is missing bounds checking on a user-supplied interface-name argument that is copied into a fixed-length stack buffer inside cmd_ipaddr_conflict. Argument length is not validated against the destination buffer before the copy, matching the [CWE-121] pattern.

Attack Vector

The attack vector is local. An authenticated user in the superadmin group invokes /usr/bin/ltsudo cmd_ipaddr_conflict with an overly long interface-name string. Because ltsudo is SUID-root, the overflow occurs inside a process running with root privileges. No verified public exploit is available. Refer to the Loytec Security Advisory for vendor-published technical details.

Detection Methods for CVE-2026-55728

Indicators of Compromise

Unexpected crash or SIGABRT termination of /usr/bin/ltsudo recorded in system logs or dmesg output.
Core dumps referencing ltsudo or the cmd_ipaddr_conflict symbol on affected LINX-A64 firmware.
Shell history or audit records showing ltsudo cmd_ipaddr_conflict invoked with abnormally long interface-name arguments.

Detection Strategies

Monitor for invocations of /usr/bin/ltsudo with argument lengths that exceed expected interface-name sizes (typically 16 characters on Linux).
Alert on repeated abnormal terminations of SUID-root binaries on Loytec devices.
Correlate superadmin account activity with local process execution to identify anomalous privileged command usage.

Monitoring Recommendations

Forward device syslog and audit logs from Loytec controllers to a centralized log platform for retention and correlation.
Track membership changes to the superadmin group and log all successful and failed ltsudo invocations.
Review vendor advisories at loytec.com/support/product-security/advisories for updated indicators.

How to Mitigate CVE-2026-55728

Immediate Actions Required

Inventory all Loytec LIP-ME201C, L-INX, L-GATE, L-ROC, L-IOB, L-DALI, L-VIS, and L-PAD devices and identify units running firmware 8.4.16 or earlier on LINX-A64.
Restrict superadmin group membership to the minimum operational set and rotate credentials for accounts that no longer need this privilege.
Apply the vendor-supplied firmware update referenced in the Loytec Security Advisory once released for your device model.

Patch Information

Loytec has published a security advisory tracking this issue. Consult the Loytec Security Advisory for the fixed firmware version, upgrade instructions, and platform-specific guidance for LINX-A64 devices.

Workarounds

Limit local shell access to Loytec devices and enforce network-layer segmentation so only trusted management hosts can reach the device management interfaces.
Reduce the number of accounts assigned to the superadmin group until a patched firmware is deployed.
Enable centralized logging on affected devices to capture any exploitation attempts against /usr/bin/ltsudo until remediation is complete.

bash

# Configuration example: audit ltsudo invocations via syslog forwarding
# Review superadmin group members on the device
getent group superadmin

# Forward local auth and system logs to a central collector
# /etc/rsyslog.d/50-loytec-forward.conf
auth,authpriv.*    @logcollector.example.internal:514
*.info;auth.none   @logcollector.example.internal:514