CVE-2022-33906 in insyde
Summary
by MITRE • 11/15/2022
DMA transactions which are targeted at input buffers used for the FwBlockServiceSmm software SMI handler could cause SMRAM corruption through a TOCTOU attack. DMA transactions which are targeted at input buffers used for the software SMI handler used by the FwBlockServiceSmm driver could cause SMRAM corruption through a TOCTOU attack. This issue was discovered by Insyde engineering based on the general description provided by Intel's iSTARE group. Fixed in kernel 5.2: 05.27.23, 5.3: 05.36.23, 5.4: 05.44.23, 5.5: 05.52.23 https://www.insyde.com/security-pledge/SA-2022048
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Analysis
by VulDB Data Team • 06/12/2026
The vulnerability described in CVE-2022-33906 represents a critical security flaw within the FwBlockServiceSmm software SMI handler that operates within the System Management Mode of x86 systems. This issue stems from improper handling of DMA transactions directed at input buffers used by the SMI handler, creating a significant attack surface that could be exploited by malicious actors with physical access to the target system. The vulnerability specifically affects systems utilizing the Insyde firmware implementation and demonstrates how firmware-level components can introduce severe security risks when not properly protected against timing-based attacks.
The technical flaw manifests through a Time-of-Check to Time-of-Use (TOCTOU) attack pattern where an attacker can manipulate data between the time a buffer is validated and when it is subsequently accessed. This vulnerability occurs when DMA transactions target input buffers used by the FwBlockServiceSmm driver, which operates in System Management Mode and has elevated privileges. The TOCTOU condition allows an attacker to modify the buffer contents between the validation check and actual usage, leading to SMRAM corruption. This type of vulnerability is particularly dangerous because it operates at the firmware level, below the operating system's protection mechanisms, and can potentially allow attackers to escalate privileges or execute arbitrary code with the highest system privileges.
The operational impact of this vulnerability extends beyond simple data corruption, as it provides a pathway for attackers to compromise the integrity of the system's firmware and potentially gain persistent access to the platform. When exploited, this vulnerability could allow an attacker with DMA capabilities to corrupt SMRAM contents, which may result in complete system compromise and the potential for privilege escalation to kernel-level or even firmware-level access. The attack requires physical access to the target system and the ability to perform DMA operations, making it a sophisticated attack vector that targets the most fundamental system components. The vulnerability's discovery by Insyde engineering through Intel's iSTARE group highlights the collaborative nature of firmware security research and the importance of cross-vendor vulnerability coordination.
The remediation for this vulnerability required firmware updates that addressed the TOCTOU condition in the FwBlockServiceSmm driver implementation. The fixes were rolled out across multiple kernel versions with specific release dates indicating the severity and urgency of the issue. This vulnerability aligns with CWE-367, which describes Time-of-Check to Time-of-Use flaws, and represents a critical concern for the ATT&CK framework under the T1068 technique for Exploitation for Privilege Escalation. The vulnerability demonstrates how firmware security is crucial for overall system security and how attacks targeting the lowest levels of system operation can bypass traditional security controls. Organizations must ensure their firmware is regularly updated and that DMA operations are properly restricted to prevent exploitation of such vulnerabilities that could lead to complete system compromise and persistent access to sensitive platform components.