CVE-2026-109971 in Red Hat
Summary
by MITRE • 10/14/2026
A flaw was found in the clevis PKCS#11 pin. The clevis-decrypt-pkcs11 script passes the PKCS#11 token PIN as a command-line argument to pkcs11-tool, making it visible to any local user through process listing or the /proc filesystem.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified in the Clevis decryption mechanism for PKCS#11 tokens represents a critical failure in credential handling and information security practices within Linux-based encryption workflows. Clevis is a decentralized automatic key management system that allows users to automatically unlock encrypted volumes using various trust mechanisms, including hardware security modules (HSMs) or smart cards via the PKCS#11 standard. The specific flaw resides in the clevis-decrypt-pkcs11 script, which is responsible for interfacing with pkcs11-tool from the OpenSC project to authenticate against a cryptographic token. Instead of utilizing secure input methods such as interactive prompts that hide user entry or environment variables passed through protected channels, the script passes the PKCS#11 token PIN directly as a command-line argument during process execution. This architectural decision fundamentally compromises the confidentiality of sensitive authentication credentials by exposing them in plain text within the operating system's process management structures.
From a technical perspective, this flaw exploits the inherent visibility of command-line arguments in modern Unix-like operating systems. When any program is executed on Linux or similar platforms, its full command line, including all passed arguments, becomes accessible to other processes running under the same user account and often to root-level users via the /proc filesystem. Specifically, entries within /proc/[pid]/cmdline expose the exact string used to invoke pkcs11-tool. Consequently, any local user with access to process listing tools such as ps or top can view the PIN in clear text while the decryption operation is underway. Furthermore, because command-line arguments are often logged by system auditing frameworks like auditd if configured for execve events, this vulnerability may also result in persistent storage of sensitive credentials on disk logs, creating a long-term exposure risk even after the process has terminated. This behavior directly contradicts established security principles regarding the protection of secrets and introduces an unnecessary attack surface that does not exist when secure input methods are employed.
The operational impact of this vulnerability is severe for environments relying on Clevis for full-disk encryption or sensitive data protection using hardware-backed keys. If an attacker gains local access to a system, even with limited privileges, they can potentially capture the PKCS#11 PIN by monitoring process arguments. Once obtained, this PIN allows the attacker to authenticate as the legitimate user against the associated cryptographic token. Depending on the configuration of the HSM or smart card, this could lead to unauthorized decryption of sensitive data stored in Clevis-encrypted volumes, extraction of private keys protected by the token, or modification of system configurations that rely on hardware-bound authentication. In high-security environments where PKCS#11 tokens are used for multi-factor authentication or strict access control, this flaw effectively neutralizes one factor of security by exposing it to local privilege escalation attacks or insider threats with minimal technical effort.
This vulnerability aligns closely with CWE-78 Improper Neutralization of Special Elements used in an OS Command and more specifically CWE-259 Use of Hard-coded Passwords if the PIN were static, but primarily maps to CWE-312 Cleartext Storage of Sensitive Information. The exposure occurs because sensitive data is stored or transmitted in a format that allows unauthorized access without decryption. In terms of offensive security frameworks, this behavior facilitates lateral movement and credential harvesting as described in MITRE ATT&CK technique T1087 Account Discovery combined with T1528 Steal Application Access Token, although here the token is replaced by direct PIN theft via process inspection. The attack vector requires local access but no additional privileges beyond what a standard user possesses to view running processes, making it particularly dangerous in multi-user systems or shared hosting environments where isolation between users may be weak.
Mitigation strategies must focus on eliminating the exposure of sensitive credentials through command-line interfaces. The most effective remediation involves modifying the clevis-decrypt-pkcs11 script and underlying pkcs11-tool integration to utilize standard input for PIN entry rather than command-line arguments. This ensures that the PIN is not visible in process listings or /proc entries, as stdin data does not appear in these system interfaces. Alternatively, if interactive prompts are undesirable due to automation requirements, environment variables should be used with strict file permissions on any scripts accessing them, ensuring they are cleared from memory immediately after use and not logged by shell history mechanisms. Organizations should also implement monitoring rules within their intrusion detection systems or host-based security agents to alert on the presence of clevis-decrypt-pkcs11 invocations containing long alphanumeric strings that resemble PINs, providing a defensive layer against exploitation while patches are applied. Updating Clevis to versions where this flaw has been addressed is essential for maintaining the integrity of hardware-backed encryption workflows and preventing unauthorized access to protected cryptographic assets through local process inspection.