CVE-2026-109976 in Red Hat
Summary
by MITRE • 10/13/2026
A flaw was found in the clevis PKCS#11 pin. The clevis-pkcs11-afunix-socket-unlock daemon crashes when an AF_UNIX client connects to the data socket without a bound address, due to an integer underflow in the getpeername result handling. This causes a denial of service, preventing LUKS disk decryption from completing during boot.
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Analysis
by VulDB Data Team • 10/13/2026
The vulnerability identified within the clevis PKCS#11 pin implementation represents a critical reliability issue affecting systems that rely on automated network-based unlocking for encrypted storage volumes via LUKS. Clevis is a decentralized system security tool designed to automatically unlock disks using various trust mechanisms, including TPMs and network-bound encryption keys. The specific component involved here is the clevis-pkcs11-afunix-socket-unlock daemon, which facilitates communication between client processes and the PKCS#11 token through an AF_UNIX socket interface. This architecture allows for secure local inter-process communication where the daemon acts as a bridge to access cryptographic keys stored in hardware or software tokens without exposing them directly to untrusted applications.
The root cause of this vulnerability lies in improper input validation within the getpeername result handling logic. When an AF_UNIX client connects to the data socket, it is expected to provide specific address information that allows the daemon to verify the identity and permissions of the connecting process. However, due to a flaw in how the length parameter for the peer name structure is processed, an integer underflow occurs if the client fails to bind a proper address before initiating the connection. This arithmetic error leads to incorrect memory access patterns or logic branches that were not anticipated by the developers, ultimately triggering a segmentation fault or similar fatal exception within the daemon process.
From a technical perspective, this flaw aligns with CWE-190, which describes integer overflow or wraparound errors. In this context, the underflow results in an invalid buffer size calculation or index value that causes the application to crash rather than gracefully rejecting the malformed connection request. The absence of robust error handling for edge cases in socket address binding allows a local user to exploit this condition simply by establishing a connection without adhering to standard addressing protocols. This lack of defensive programming practices means that any process with access to the specific AF_UNIX socket can trigger the crash, regardless of its privilege level, provided it can reach the socket file system path.
The operational impact of this vulnerability is significant for environments relying on automated boot processes involving network-bound encryption keys. Since the clevis daemon crashes upon receiving such a connection attempt, the entire decryption workflow is interrupted. During system startup, if the operating system attempts to unlock the root filesystem or other critical volumes using Clevis and encounters this failure state, the boot process will halt or fail completely. This results in a denial of service condition where legitimate users are unable to access their systems because the cryptographic infrastructure required for authentication has become unavailable due to the daemon's termination.
This issue also reflects weaknesses categorized under ATT&CK technique T1053, specifically related to scheduled tasks or startup scripts that may be disrupted by system instability, although more directly it impacts availability through service disruption. The vulnerability underscores the importance of strict input validation and bounds checking in low-level system services that handle cryptographic operations. Even though the trigger requires a local connection, the ability to crash a critical security daemon highlights gaps in resilience design for infrastructure components that are expected to remain stable under all valid and invalid interaction scenarios.
Mitigation strategies should focus on updating the clevis-pkcs11 package to versions where this integer handling logic has been corrected. Developers must ensure that the length parameter derived from getpeername is validated against maximum buffer sizes before being used in memory operations or loop conditions. Additionally, implementing strict socket address binding requirements for clients connecting to sensitive AF_UNIX sockets can prevent such malformed requests from reaching vulnerable code paths. System administrators should monitor for updates to clevis and related PKCS#11 modules to restore full availability of automated disk decryption capabilities during boot sequences.