CVE-2025-22047 in Linux
Summary
by MITRE • 04/16/2025
In the Linux kernel, the following vulnerability has been resolved:
x86/microcode/AMD: Fix __apply_microcode_amd()'s return value
When verify_sha256_digest() fails, __apply_microcode_amd() should propagate the failure by returning false (and not -1 which is promoted to true).
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Analysis
by VulDB Data Team • 02/15/2026
The vulnerability identified as CVE-2025-22047 resides within the x86 microcode handling subsystem of the Linux kernel, specifically affecting AMD processor microcode application mechanisms. This flaw represents a critical issue in the kernel's firmware update processing logic that could potentially compromise system integrity and security. The vulnerability manifests in the __apply_microcode_amd() function which is responsible for applying microcode updates to AMD processors during system operation or boot processes. The function's improper handling of error conditions creates a scenario where failure states are not correctly communicated to calling functions, potentially leading to incorrect system behavior and security implications.
The technical root cause of this vulnerability stems from an incorrect return value assignment within the microcode application logic. When the verify_sha256_digest() function fails to validate the cryptographic integrity of a microcode update, the __apply_microcode_amd() function should return a boolean false value to indicate failure. However, the current implementation returns the integer value -1 instead of false, which when promoted to a boolean context evaluates to true. This misinterpretation of failure states creates a logical error where the system incorrectly believes a microcode update was successfully applied even when cryptographic verification has failed. The issue represents a classic case of improper error handling and type conversion that violates fundamental security principles for firmware validation processes.
The operational impact of this vulnerability extends beyond simple functional failure, potentially creating security risks that align with CWE-252, which addresses "Unchecked Return Value" in software security. An attacker could exploit this vulnerability by crafting malicious microcode updates that pass the initial validation but fail the cryptographic verification step. When the system incorrectly processes these updates, it could lead to system instability, performance degradation, or potentially create opportunities for privilege escalation attacks. The vulnerability particularly affects systems running Linux kernels with AMD processors that utilize microcode updates, making it relevant to a broad range of enterprise and consumer computing environments. This flaw could be leveraged in supply chain attacks where malicious actors attempt to inject compromised microcode updates that appear legitimate but contain hidden malicious code.
The mitigation strategy for CVE-2025-22047 involves applying the kernel patch that corrects the return value handling in the __apply_microcode_amd() function. This patch ensures that when verify_sha256_digest() fails, the function properly returns false instead of -1, thereby maintaining correct error propagation throughout the microcode application stack. System administrators should prioritize updating their kernel versions to include this fix, particularly in environments where microcode updates are frequently applied or where security compliance requirements mandate strict firmware validation. The fix aligns with ATT&CK technique T1014, which addresses "Rootkit" and firmware manipulation, as proper microcode validation is essential for preventing low-level system compromise. Organizations should also implement monitoring procedures to detect any anomalous microcode update behavior and ensure that their firmware update processes maintain proper cryptographic integrity verification throughout the entire update lifecycle.