CVE-2026-72895: Siemens SIMATIC IPC Privilege Escalation

CVE-2026-72895 Overview

CVE-2026-72895 is a UEFI Secure Boot bypass affecting multiple Siemens SIMATIC Industrial PC (IPC) product lines. A BIOS vendor test key was left in the UEFI Secure Boot key database on shipped devices. An attacker with physical or administrative access can boot an operating system or UEFI application signed with that test key. This defeats Secure Boot protections even when the feature is enabled. Successful exploitation results in full loss of device confidentiality, integrity, and availability. The weakness is tracked as CWE-1394: Use of Default Cryptographic Key.

Critical Impact
Attackers with local access can load unsigned or attacker-signed boot payloads on affected SIMATIC IPC devices, enabling bootkit installation and persistent compromise beneath the operating system.

Affected Products

Siemens SIMATIC IPC BX-21A (All versions prior to V31.01.13)
Siemens SIMATIC IPC RW-543A (All versions prior to V1.1.4)
Siemens SIMATIC IPC227G / IPC277G / IPC277G PRO / IPC327G / IPC377G (All versions prior to V28.01.15)

Discovery Timeline

2026-10-13 - CVE-2026-72895 published to NVD
2026-10-15 - Last updated in NVD database

Technical Details for CVE-2026-72895

Vulnerability Analysis

UEFI Secure Boot validates every boot-stage binary against keys stored in the platform's authorized signature database (db). Any binary signed by a key present in db is considered trusted and permitted to execute during the boot chain. Siemens shipped the affected SIMATIC IPC devices with a BIOS vendor test key included in db. Because the private half of a test key is typically distributed with reference BIOS tooling, it must be treated as publicly known.

An attacker who can sign a bootloader, UEFI driver, or UEFI application with that test key produces an artifact the firmware accepts. The platform therefore executes attacker-controlled code before the operating system kernel, hypervisor, or endpoint sensors load.

Root Cause

The root cause is an insecure default configuration in the Secure Boot trust anchor set, consistent with [CWE-1394]. The shipped db contained a non-production vendor test certificate that should have been removed before manufacturing release. Secure Boot's cryptographic design is sound; the trust database it relies upon was provisioned with a key whose private material is not controlled by Siemens or the device owner.

Attack Vector

Exploitation requires local access, either physical or administrative. An administrator with the ability to write to the EFI System Partition can place a malicious .efi binary signed with the known test key and configure the platform to boot it. An attacker with physical access can achieve the same outcome through removable boot media. Once the attacker-signed payload runs, it can install a UEFI bootkit, disable firmware-based attestation, patch the OS loader, or implant persistence that survives operating system reinstallation. User interaction is required to reboot the device into the malicious payload.

No public proof-of-concept is listed, and the vulnerability is not present on the CISA Known Exploited Vulnerabilities list. The EPSS score at publication is low, reflecting the local-access precondition.

Detection Methods for CVE-2026-72895

Indicators of Compromise

Presence of a BIOS vendor test certificate in the UEFI db variable on affected SIMATIC IPC hardware.
Unexpected .efi binaries in the EFI System Partition that validate against the test certificate rather than the Siemens or Microsoft production keys.
Boot configuration data (BCD or efibootmgr) entries referencing unknown loaders or non-standard paths.
Mismatch between TPM PCR0–PCR7 measurements and the known-good baseline for the device model and firmware version.

Detection Strategies

Enumerate the Secure Boot key database on each device using mokutil --db on Linux or Get-SecureBootUEFI db in PowerShell and compare against a hardened baseline that excludes the test key.
Validate boot chain integrity using TPM remote attestation and alert on PCR values that drift from the expected measurement for the installed firmware.
Hunt for newly created or modified files in the EFI System Partition (/boot/efi or the Windows ESP) and verify signer identity.

Monitoring Recommendations

Centralize UEFI firmware version, Secure Boot state, and db/dbx contents in your endpoint telemetry pipeline for continuous drift detection.
Monitor for anomalous reboots, boot order changes, and attempts to disable Secure Boot or clear platform keys.
Correlate administrative logons on SIMATIC IPC devices with subsequent firmware or boot-partition activity.

How to Mitigate CVE-2026-72895

Immediate Actions Required

Inventory all affected SIMATIC IPC BX-21A, RW-543A, and IPC227G/277G/277G PRO/327G/377G devices and record current BIOS versions.
Apply the Siemens firmware updates: V31.01.13 for IPC BX-21A, V1.1.4 for IPC RW-543A, and V28.01.15 for the IPC227G/277G/327G/377G family.
Restrict physical access to affected IPC hardware and enforce BIOS setup passwords to block boot-order tampering.
Review and tighten administrative access to the operating systems running on these devices.

Patch Information

Siemens published advisory SSA-159454 with fixed firmware for each affected product line. The updates remove the BIOS vendor test key from the Secure Boot db. Verify after update that the test certificate is no longer enrolled and that dbx entries revoke any previously trusted test-signed binaries where provided.

Workarounds

Where immediate patching is not feasible, disable booting from removable media in BIOS and set a strong BIOS administrator password.
Enable TPM-backed measured boot and remote attestation so that unexpected boot-stage binaries are detected post-boot.
Enforce full-disk encryption bound to TPM PCRs so that a boot-chain modification invalidates key release and blocks data access.
Physically secure industrial deployments and restrict administrative Windows or Linux accounts on the IPC to the minimum operational set.

bash

# Verify Secure Boot state and inspect enrolled db keys on Linux
mokutil --sb-state
mokutil --db | less

# On Windows, confirm Secure Boot is on and list db contents
Confirm-SecureBootUEFI
Get-SecureBootUEFI -Name db | Format-List