CVE-2022-21505: Oracle Linux Privilege Escalation Flaw

CVE-2022-21505 Overview

CVE-2022-21505 is a Linux kernel security flaw that allows an attacker to bypass the kernel lockdown mechanism. The vulnerability resides in the Integrity Measurement Architecture (IMA) subsystem. When IMA appraisal is configured with the ima_appraise=log boot parameter, an authenticated local attacker can defeat lockdown using kexec on systems where Secure Boot is disabled or unavailable. IMA blocks the use of ima_appraise=log when Secure Boot is enabled, but the same restriction does not extend to lockdown without Secure Boot. The flaw is categorized under [CWE-346] (Origin Validation Error) and affects Oracle Linux versions 7, 8, and 9.

Critical Impact
A local attacker with elevated privileges can bypass kernel lockdown protections, load unsigned kernel images via kexec, and compromise the confidentiality, integrity, and availability of the system.

Affected Products

Oracle Linux 7
Oracle Linux 8
Oracle Linux 9

Discovery Timeline

2024-12-24 - CVE-2022-21505 published to NVD
2025-06-18 - Last updated in NVD database

Technical Details for CVE-2022-21505

Vulnerability Analysis

The Linux kernel implements a lockdown feature that restricts privileged userspace operations capable of modifying the running kernel. Lockdown can be enforced independently or in conjunction with Secure Boot. IMA appraisal validates file integrity using cryptographic signatures and can be configured in enforcement or log-only mode through the ima_appraise= boot parameter.

The kernel correctly prevents setting ima_appraise=log when Secure Boot is enabled. However, the check does not extend to scenarios where lockdown is active without Secure Boot. This gap allows an attacker with sufficient privileges to invoke kexec_file_load and load an unsigned or modified kernel image, defeating lockdown's promise of preventing kernel modification.

Root Cause

The root cause is an origin validation error in IMA's boot parameter handling logic. The validation logic ties the ima_appraise=log restriction to Secure Boot state rather than to the broader lockdown mode. The fix is committed upstream as 543ce63b664e2c2f9533d089a4664b559c3e6b5b in the Kernel Git Commit Log, which extends the restriction to cover lockdown configurations independently.

Attack Vector

Exploitation requires local access and high privileges on the target system. The attacker boots the system with the ima_appraise=log parameter or leverages an existing configuration where this parameter is set. With lockdown active but Secure Boot disabled, the attacker uses kexec to load an arbitrary kernel image. IMA logs the appraisal failure rather than blocking the operation, allowing the unsigned kernel to be executed and bypassing lockdown's integrity guarantees.

No verified public exploit code is available for this issue. Technical details are documented in the upstream kernel commit referenced above.

Detection Methods for CVE-2022-21505

Indicators of Compromise

Presence of ima_appraise=log in kernel boot parameters on systems where Secure Boot is disabled. Inspect /proc/cmdline and bootloader configuration files such as /boot/grub2/grub.cfg.
Unexpected kexec_load or kexec_file_load syscall activity originating from privileged user sessions.
IMA audit log entries indicating appraisal failures without enforcement action, visible in /var/log/audit/audit.log with type=INTEGRITY_DATA records.

Detection Strategies

Audit kernel command-line arguments at boot and at runtime to identify hosts running with ima_appraise=log while lockdown is active and Secure Boot is off.
Monitor for invocations of kexec binaries and related syscalls correlated with administrative sessions and boot configuration changes.
Compare installed kernel package versions against vendor-published fixed versions to identify unpatched hosts across the fleet.

Monitoring Recommendations

Forward kernel audit logs and IMA appraisal events to a centralized logging or SIEM platform for correlation.
Establish baseline boot parameters for production hosts and alert on deviations introduced through configuration drift or unauthorized modification.
Track Secure Boot and lockdown status across systems and flag hosts where lockdown is enabled without Secure Boot enforcement.

How to Mitigate CVE-2022-21505

Immediate Actions Required

Apply the kernel update provided by Oracle for the affected Oracle Linux 7, 8, and 9 releases. Refer to the Oracle CVE-2022-21505 Detail advisory for package versions.
Remove the ima_appraise=log parameter from bootloader configurations unless explicitly required for diagnostic purposes.
Enable Secure Boot in firmware where hardware supports it to enforce additional integrity checks alongside lockdown.

Patch Information

The upstream fix is available in the mainline Linux kernel as commit 543ce63b664e2c2f9533d089a4664b559c3e6b5b. The patch ensures that IMA blocks the ima_appraise=log setting whenever lockdown is active, not only when Secure Boot is enabled. Oracle has issued corresponding kernel package updates documented in its advisory portal.

Workarounds

Restrict physical and remote administrative access to systems where Secure Boot cannot be enabled, since exploitation requires high privileges and local access.
Configure bootloader passwords to prevent unauthorized modification of kernel boot parameters at boot time.
Disable kexec functionality on production systems that do not require live kernel replacement by setting kernel.kexec_load_disabled=1 via sysctl.

bash

# Disable kexec_load to mitigate exploitation paths
echo 'kernel.kexec_load_disabled=1' | sudo tee /etc/sysctl.d/99-kexec-lockdown.conf
sudo sysctl --system

# Verify the current kernel command line for the offending parameter
cat /proc/cmdline | grep -o 'ima_appraise=[^ ]*'