CVE-2026-109969 in Red Hat
Summary
by MITRE • 10/14/2026
A flaw was found in the clevis PKCS#11 pin. The clevis-pkcs11-afunix-socket-unlock daemon creates AF_UNIX sockets without explicit permission restrictions or peer credential verification. Under a permissive process umask, any local user can connect to the control socket and inject arbitrary device/key pairs, or connect to the data socket to receive LUKS passphrases.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified in clevis-pkcs11-afunix-socket-unlock represents a critical failure in access control mechanisms for inter-process communication sockets on Linux systems utilizing disk encryption via LUKS and Clevis network-bound decryption. This flaw specifically affects the daemon responsible for managing PKCS#11 tokens within the Clevis framework, which is commonly deployed to automate the unlocking of encrypted volumes using hardware security modules or remote key servers. The core technical deficiency lies in the creation of AF_UNIX domain sockets without implementing explicit permission restrictions or verifying peer credentials during connection establishment. In Unix-like operating systems, file permissions and socket access controls are often governed by the process umask setting if not explicitly defined within the application code. When a permissive umask is active, which allows group or other users to read or write files created by the process, the resulting sockets inherit these overly broad permissions rather than restricting access solely to authorized processes such as systemd-logind or specific system services.
This architectural oversight enables any local user on the affected system to interact with the Clevis daemon's control and data interfaces without authentication. By connecting to the exposed control socket, an attacker can inject arbitrary device mappings or key pairs into the decryption pipeline, effectively bypassing intended security boundaries. More critically, connection to the data socket allows a malicious actor to receive LUKS passphrases in plaintext. Since these passphrases are essential for decrypting sensitive volumes containing personal identifiable information, financial records, intellectual property, and other classified data, their exposure constitutes a severe compromise of confidentiality. The attacker does not need elevated privileges or prior exploitation of another vulnerability; simple local user access is sufficient to exploit this flaw due to the lack of socket-level isolation.
From an industry standard perspective, this vulnerability aligns with CWE-732: Incorrect Permission Assignment for Critical Resource, as it involves improper assignment of permissions that allow unauthorized actors to perform actions or access data. It also relates closely to CWE-284: Improper Access Control, where the system fails to restrict interactions between processes based on identity and privilege levels. In terms of offensive security frameworks such as MITRE ATT&CK, this flaw facilitates lateral movement and credential harvesting within a local environment. An attacker leveraging this vulnerability would be engaging in techniques associated with T1059: Command and Scripting Interpreter or potentially T1552: Unsecured Credentials if the goal is to extract stored secrets for further exploitation across networked systems that rely on these encrypted volumes for secure storage of credentials or keys.
The operational impact extends beyond immediate data theft, as it undermines the trust model of automated decryption solutions like Clevis and LUKS. Organizations relying on these tools for compliance with standards such as NIST SP 800-111 regarding encryption key management may find their security posture significantly weakened if this vulnerability is present in production environments. The ability to intercept passphrases allows attackers to decrypt volumes at rest, potentially leading to data breaches that violate regulatory requirements like GDPR or HIPAA depending on the jurisdiction and data type involved. Furthermore, because Clevis often integrates with TPMs (Trusted Platform Modules) for hardware-backed key storage, compromising the software layer via this socket vulnerability can negate the benefits of hardware security features if the attacker can manipulate the decryption flow before it reaches the secure element.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The most effective solution is to upgrade clevis-pkcs11-afunix-socket-unlock to a patched version where developers have implemented explicit socket permission checks, such as using setsockopt with SO_PEERCRED or implementing Unix domain socket access control lists (ACLs) that restrict connections to specific UIDs and GIDs. System administrators should also enforce strict umask settings for services running under dedicated service accounts, ensuring that newly created sockets default to restrictive permissions like 0600 rather than inheriting permissive defaults from the environment. Additionally, enabling SELinux or AppArmor profiles can provide mandatory access control layers that prevent unauthorized processes from connecting to these sockets even if file system permissions are misconfigured. Regular auditing of socket permissions and monitoring for unexpected connections to Clevis-related services should be integrated into security operations center workflows to detect potential exploitation attempts in real time.