CVE-2026-82018 in IGEL
Summary
by MITRE • 08/29/2026
IGEL OS 12 before 12.9.0, 12.8.3 LTS and IGEL OS 11 before 11.11.150 contain a secure boot bypass vulnerability in the GRUB boot stage that allows physically present attackers to gain unauthorized root access by placing an unsigned empty file named igel.conf on a partition. Attackers can exploit GRUB's fail-open signature verification behavior to drop into an interactive GRUB prompt, then boot the device's own kernel with additional command-line arguments to obtain a root shell with the disk unlocked while leaving TPM PCR values unaltered.
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Analysis
by VulDB Data Team • 08/29/2026
The vulnerability identified in IGEL OS versions prior to 12.9.0 and 12.8.3 LTS, as well as version 11 before 11.11.150, represents a critical failure in the secure boot chain specifically within the GRUB bootloader stage. This flaw allows physically present attackers to bypass security controls designed to prevent unauthorized modifications to the system's startup process. The core of the issue lies in how GRUB handles signature verification during the early boot sequence. When an attacker places an unsigned, empty file named igel.conf on a partition accessible by the bootloader, it triggers a specific behavior where GRUB fails open rather than failing closed or halting execution entirely. This design choice effectively neutralizes the integrity checks that are supposed to ensure only signed and trusted code is executed during boot, thereby creating a pathway for unauthorized access.
From an operational perspective, this vulnerability enables a sophisticated attack vector that goes beyond simple physical tampering. An attacker with physical access can exploit the fail-open behavior of GRUB's signature verification mechanism to interrupt the normal boot process and drop into an interactive GRUB command prompt. Once inside this environment, the attacker is not merely viewing system information but gains the ability to manipulate kernel parameters directly. By injecting additional command-line arguments during the boot sequence, the attacker can force the operating system to start with elevated privileges or without certain security restrictions. This manipulation allows the acquisition of a root shell while simultaneously ensuring that the disk remains unlocked and accessible, effectively bypassing encryption protections intended to protect data at rest.
A particularly concerning aspect of this exploit is its ability to maintain stealth regarding hardware-based integrity measurements. The attack leaves Trusted Platform Module (TPM) Platform Configuration Register (PCR) values unaltered. This means that standard remote attestation mechanisms or local integrity checks relying on TPM PCR logs may not detect the compromise, as the measured boot state appears consistent with a legitimate startup sequence despite the presence of unauthorized modifications and elevated access. This characteristic makes detection significantly more difficult for security monitoring tools that rely solely on static measurements without analyzing runtime behavior or command-line arguments passed to the kernel.
The technical classification of this vulnerability aligns closely with CWE-284, which describes Improper Access Control, specifically in contexts where authentication or authorization mechanisms are bypassed through configuration manipulation rather than code execution flaws. Furthermore, from a tactical standpoint as defined by the MITRE ATT&CK framework, this exploit maps to T1503.002, Use of Trusted Relocation Environment (TREE), and potentially T1499, Endpoint Denial of Service if the boot process is disrupted, though the primary intent here is unauthorized access rather than disruption. It also relates to T1608, Install Malicious Image, as it involves modifying the boot environment to gain persistent or immediate high-level privileges without installing traditional malware binaries in user space.
Mitigation strategies must address both the software configuration and physical security postures of affected systems. The primary remediation is to apply the vendor-provided patches that update IGEL OS to version 12.9.0, 12.8.3 LTS, or 11.11.150 respectively, as these versions contain fixes for the GRUB configuration handling logic. Organizations should also review their BIOS/UEFI settings to ensure that secure boot is strictly enforced and configured to fail closed on signature verification errors rather than failing open where possible. Additionally, physical access controls are paramount; since this attack requires physical presence, restricting access to server rooms or device locations remains a critical defense layer. Implementing strict policies around USB port usage can also help prevent the placement of malicious configuration files like igel.conf on external media that might be used during boot attempts. Regular auditing of bootloader configurations and monitoring for unexpected changes in GRUB environment variables can further enhance detection capabilities against such low-level exploits.