CVE-2026-109968 Overview
CVE-2026-109968 is an information disclosure flaw in the clevis PKCS#11 pin component. The clevis-pkcs11-afunix-socket-unlock daemon writes Linux Unified Key Setup (LUKS) disk encryption passphrases in plaintext to a log file. The log file is created without restrictive permissions and inherits the default process umask, leaving it world-readable. A local attacker with any shell access on the system can read the log file and recover the LUKS passphrase. This weakness is categorized under [CWE-532: Insertion of Sensitive Information into Log File].
Critical Impact
A local, authenticated user can read a world-readable log file to recover LUKS full-disk encryption passphrases, breaking confidentiality of encrypted volumes.
Affected Products
- Clevis PKCS#11 pin (clevis-pkcs11-afunix-socket-unlock daemon)
- Red Hat distributions shipping the affected clevis package
- Systems using clevis PKCS#11 automated LUKS unlocking
Discovery Timeline
- 2026-10-14 - CVE CVE-2026-109968 published to the National Vulnerability Database
- 2026-10-14 - Last updated in NVD database
Technical Details for CVE-2026-109968
Vulnerability Analysis
Clevis is a pluggable framework for automated decryption, commonly used to unlock LUKS-encrypted volumes at boot without manual passphrase entry. The PKCS#11 pin provides unlock support using hardware tokens through a helper daemon, clevis-pkcs11-afunix-socket-unlock, that communicates over an AF_UNIX socket.
During normal operation, the daemon handles the recovered LUKS passphrase so it can be forwarded to cryptsetup for volume unlock. The daemon writes diagnostic output that includes the passphrase in cleartext to a log file on disk. The passphrase remains readable in the log after boot completes.
The daemon creates the log file with the inherited process umask rather than an explicit restrictive mode. On a default system this produces file permissions such as 0644, which allows any local account to open and read the file. Any user who can log in locally or run code as an unprivileged service account can read the LUKS passphrase.
Root Cause
The root cause is twofold. First, the daemon logs sensitive key material that should never be persisted to disk. Second, the log file is opened without an explicit mode argument or a tightened umask, so permissions default to world-readable. These are classic [CWE-532] conditions where authentication secrets are exposed through observability output.
Attack Vector
Exploitation requires local access with low privileges and no user interaction. An attacker with a shell on the host, including an account obtained through a separate initial-access vulnerability, reads the log file path produced by the daemon and extracts the plaintext passphrase. Once the passphrase is known, the attacker can decrypt the LUKS volume offline on another system, undermining full-disk encryption as a defense against device theft or forensic recovery.
No verified public exploit code is available. The behavior is reproduced by reviewing the daemon's log output on an affected system.
Detection Methods for CVE-2026-109968
Indicators of Compromise
- Presence of a log file produced by clevis-pkcs11-afunix-socket-unlock with permissions 0644 or any mode granting read access to other.
- Log lines emitted by the daemon containing passphrase or key material in plaintext.
- Access by non-root accounts to clevis daemon log paths, visible in audit logs.
Detection Strategies
- Audit filesystems for files owned by root under clevis runtime or log directories and flag any with world-readable permission bits.
- Enable Linux audit rules on the daemon log path to record open and read syscalls by non-root UIDs.
- Scan historical log content for the specific message format the daemon uses when writing recovered secrets.
Monitoring Recommendations
- Forward auditd and journald events for clevis-pkcs11-afunix-socket-unlock to a centralized log platform for retention and correlation.
- Alert on any process other than root reading log files created by the clevis daemon.
- Track package versions of clevis across the fleet to confirm patched builds are deployed everywhere PKCS#11 unlock is used.
How to Mitigate CVE-2026-109968
Immediate Actions Required
- Rotate any LUKS passphrase that may have been written to the daemon log file on affected hosts.
- Delete or securely wipe existing clevis-pkcs11-afunix-socket-unlock log files containing plaintext secrets.
- Restrict permissions on any remaining log file to 0600 owned by root until a patched package is installed.
- Review local accounts and service identities with shell or filesystem read access on affected hosts.
Patch Information
Refer to the Red Hat CVE-2026-109968 Advisory and Red Hat Bug #2462394 Details for the authoritative list of fixed package versions and errata. Update the clevis package to a build that removes passphrase logging and creates log files with restrictive permissions.
Workarounds
- Stop and disable the clevis-pkcs11-afunix-socket-unlock daemon on hosts that do not require PKCS#11-based LUKS unlock.
- Set an explicit restrictive umask such as 0077 for the service unit to force non-world-readable file creation.
- Redirect the daemon log output to a directory with mode 0700 owned by root and rotate aggressively to limit exposure.
- Treat any host where the daemon has previously run as having a disclosed passphrase and plan key rotation accordingly.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.