CVE-2026-104618 in Linux Enterprise Server
Summary
by MITRE • 10/15/2026
On request the `sdbootutil` script creates a world-readable debug log in /var/log/sdbootutil.log. The log file is created world-readable, however, which means that arbitrary low-privileged users in the system will be able to extract secrets from it.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified involves an improper access control mechanism within the sdbootutil script, specifically concerning the creation and permission settings of its debug logging facility. When invoked, this utility generates a log file located at /var/log/sdbootutil.log with world-readable permissions. This configuration error allows any user account on the system, regardless of privilege level or authentication status, to read the contents of this file. In many embedded Linux environments and systems utilizing systemd-boot utilities, boot processes often involve sensitive operations such as verifying cryptographic signatures, handling encryption keys for disk decryption, or logging secure boot states. Consequently, a log file generated during these phases may contain high-value secrets, including private key material, passphrase fragments, token values, or detailed information about the system's security posture that should remain restricted to privileged processes only.
From a technical perspective, this flaw represents a classic instance of insecure default permissions where sensitive data is exposed due to insufficient restriction on file access modes. The operating system’s discretionary access control model permits read operations for all users because the file mode bits are set incorrectly during creation or by subsequent script logic that fails to apply restrictive umask settings or explicit chmod calls with restricted groups. This lack of segregation between privileged operational logs and general user-accessible files violates fundamental security principles regarding data confidentiality. The presence of such information in a world-readable location effectively neutralizes the protection offered by other system hardening measures, as an attacker does not need to exploit a separate privilege escalation vulnerability to access this sensitive data; they simply need local shell or console access at any level below root.
The operational impact of this vulnerability is significant, particularly in environments where physical or low-level logical access can be achieved by malicious actors. An adversary with even minimal user privileges could extract cryptographic secrets that are critical for maintaining the integrity and confidentiality of the system’s storage. If these logs contain private keys used for secure boot verification or disk encryption, their exposure allows an attacker to potentially bypass authentication mechanisms, decrypt stored data offline, or forge valid boot images to load malicious kernels without detection. This undermines the trust chain established by secure boot implementations and compromises the overall security posture of the device. In multi-tenant systems or shared computing environments, this flaw could lead to cross-user information leakage, violating isolation boundaries between different user accounts on the same host.
This vulnerability aligns with CWE-732: Incorrect Permission Assignment for Critical Resource, as it involves assigning overly permissive access rights to a file containing sensitive operational data. It also relates to CWE-538: Insertion of Sensitive Information into Log File, since debug logs are inadvertently capturing and exposing secrets that should be omitted or protected through encryption and strict access controls. From an offensive security perspective, this behavior facilitates reconnaissance and credential harvesting phases in the MITRE ATT&CK framework, specifically under techniques such as T1083: File and Directory Discovery and potentially T1552.004: Unsecured Credentials if private keys or passwords are logged. Remediation requires immediate correction of the file permission settings to ensure that /var/log/sdbootutil.log is accessible only by the root user or a specific privileged group responsible for log management. Additionally, developers should audit the sdbootutil script and similar utilities to prevent sensitive data from being written to logs in the first place, employing logging best practices that exclude credentials, keys, and other high-value secrets from debug output unless explicitly required and properly secured through encryption at rest or memory-only handling.