CVE-2026-46748: SINEC INS Privilege Escalation Vulnerability

CVE-2026-46748 Overview

CVE-2026-46748 is a local privilege escalation vulnerability in Siemens SINEC INS affecting all versions prior to V1.0 SP2 Update 6. The flaw stems from a binary configured with the cap_dac_override Linux capability, which permits the process to bypass discretionary access control file system permission checks. A local attacker with low-privilege access can leverage this misconfiguration to read or modify arbitrary files, ultimately gaining root privileges on the affected system. The weakness is categorized as [CWE-250] Execution with Unnecessary Privileges. Siemens has published advisory SSA-860189 addressing the issue.

Critical Impact
A local attacker can bypass file system permission checks through a misconfigured Linux capability, leading to arbitrary file modification and full root compromise of SINEC INS hosts.

Affected Products

Siemens SINEC INS — all versions prior to V1.0 SP2 Update 6

Discovery Timeline

2026-06-09 - CVE-2026-46748 published to NVD
2026-06-09 - Last updated in NVD database

Technical Details for CVE-2026-46748

Vulnerability Analysis

The vulnerability resides in the Siemens SINEC INS (Infrastructure Network Services) platform, which centralizes network services such as RADIUS, syslog, and DHCP. A binary shipped with SINEC INS is granted the Linux cap_dac_override capability. This capability allows the process to bypass Discretionary Access Control (DAC) checks for read, write, and execute operations on any file on the system.

When a process holds cap_dac_override, the kernel skips standard owner, group, and other permission verification. If the binary exposes any user-controlled file path operation, an attacker who can invoke it inherits this permission bypass. This effectively converts a low-privileged user into one capable of modifying root-owned files.

Root Cause

The root cause is an over-privileged binary [CWE-250]. Granting cap_dac_override violates the principle of least privilege because the binary requires broader file system access than necessary for its intended function. The capability is persistent and applies to every invocation, regardless of the calling user.

Attack Vector

An authenticated local attacker with limited shell access executes the over-privileged binary and directs it to operate on sensitive targets such as /etc/shadow, /etc/sudoers, or systemd unit files. By overwriting these files, the attacker installs a backdoor account or replaces a service binary that runs as root, achieving privilege escalation on the next privileged invocation.

// No verified public exploit code is available.
// Conceptually, exploitation involves invoking the cap_dac_override-enabled
// binary to write attacker-controlled content to a root-owned file such as
// /etc/passwd or a script executed by a privileged systemd service.
// Refer to Siemens advisory SSA-860189 for vendor-confirmed technical details.

Detection Methods for CVE-2026-46748

Indicators of Compromise

Unexpected modifications to root-owned files such as /etc/passwd, /etc/shadow, /etc/sudoers, or files under /etc/systemd/.
New or modified cron entries, SSH authorized_keys files, or PAM configuration on SINEC INS hosts.
Execution of SINEC INS binaries by non-administrative local users followed by privileged file writes.

Detection Strategies

Enumerate binaries with elevated capabilities using getcap -r / 2>/dev/null and alert on any binary holding cap_dac_override.
Enable Linux audit rules (auditd) on sensitive files to log writes performed by non-root UIDs that bypass DAC.
Correlate execve events of the affected binary with subsequent file modification events on protected paths.

Monitoring Recommendations

Forward auditd and process execution telemetry from SINEC INS hosts to a centralized analytics platform for behavioral baselining.
Monitor for privilege transitions and anomalous local user activity on industrial network management hosts.
Track integrity of critical configuration files using file integrity monitoring (FIM) with cryptographic hashes.

How to Mitigate CVE-2026-46748

Immediate Actions Required

Upgrade SINEC INS to V1.0 SP2 Update 6 or later as directed in Siemens advisory SSA-860189.
Restrict local shell and interactive access to SINEC INS hosts to trusted administrators only.
Audit existing accounts on affected systems and remove any unauthorized users created prior to patching.

Patch Information

Siemens has released SINEC INS V1.0 SP2 Update 6 to remediate CVE-2026-46748. The fix removes the unnecessary cap_dac_override capability from the affected binary, eliminating the DAC bypass primitive. Customers should consult the Siemens Security Advisory SSA-860189 for download instructions and version-specific guidance.

Workarounds

If patching is not immediately feasible, manually remove the capability using setcap -r <binary> after verifying functional impact in a test environment.
Limit local logon rights on SINEC INS hosts to administrative personnel and enforce strong authentication.
Apply network segmentation around SINEC INS management hosts to reduce the population of users that could attempt local exploitation.

bash

# Identify binaries with cap_dac_override on the host
sudo getcap -r / 2>/dev/null | grep cap_dac_override

# Remove file capabilities from a specific binary (test before production use)
sudo setcap -r /path/to/affected/binary

# Verify capability removal
sudo getcap /path/to/affected/binary