CVE-2022-33985 in insyde
Summary
by MITRE • 11/15/2022
DMA transactions which are targeted at input buffers used for the NvmExpressDxe 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 NvmExpressDxe 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. This issue was fixed in kernel 5.2: 05.27.25, kernel 5.3: 05.36.25, kernel 5.4: 05.44.25, kernel 5.5: 05.52.25 https://www.insyde.com/security-pledge/SA-2022055
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Analysis
by VulDB Data Team • 06/12/2026
The vulnerability identified as CVE-2022-33985 represents a critical security flaw within the NvmExpressDxe driver's software SMI handler implementation, specifically targeting the Secure Memory Ranges (SMRAM) within UEFI firmware environments. This issue arises from improper handling of DMA transactions directed at input buffers used by the driver's SMI handler, creating a window of opportunity for sophisticated attackers to exploit temporal inconsistencies in memory access patterns. The vulnerability manifests through a Time-of-Check to Time-of-Use (TOCTOU) attack vector that allows adversaries to manipulate memory contents between the initial validation phase and the actual execution phase, ultimately leading to SMRAM corruption that compromises the integrity of the firmware's protected memory regions.
The technical implementation of this vulnerability stems from the NvmExpressDxe driver's insufficient validation mechanisms when processing DMA transactions within the software SMI handler context. During normal operation, the driver receives input buffers through DMA transfers that are subsequently processed by the SMI handler to manage NVMe storage operations. However, the flaw occurs when the system performs a check on buffer contents or memory state at one point in time, but then executes operations on potentially modified data at a later point. This temporal gap enables attackers to modify the DMA target memory between the check and use phases, allowing them to redirect execution flow or corrupt memory structures within SMRAM. The vulnerability specifically affects systems where the NvmExpressDxe driver operates in SMI context, which provides privileged access to system memory and hardware resources.
The operational impact of this vulnerability extends beyond simple data corruption, as it represents a serious threat to firmware security and system integrity. Successful exploitation can result in complete system compromise, as SMRAM corruption allows attackers to bypass traditional security mechanisms and execute arbitrary code with the highest privilege levels available within the firmware environment. This capability enables attackers to establish persistent backdoors, modify firmware images, or extract sensitive information from system memory. The vulnerability's exploitation requires a sophisticated attack setup involving DMA capabilities and precise timing control, but once achieved, it provides attackers with an effective means to subvert system security. The issue affects various kernel versions including 5.2 through 5.5, indicating it was a widespread problem across multiple firmware implementations.
The remediation for this vulnerability required specific updates to kernel versions, with fixes released in kernel versions 5.2.25, 5.3.25, 5.4.25, and 5.5.25, as documented by Insyde engineering. These updates implemented proper synchronization mechanisms and enhanced validation procedures to prevent the TOCTOU conditions that enabled the SMRAM corruption. The fix addresses the root cause by ensuring that input buffer validation occurs in a manner that prevents modification between the check and use phases, effectively closing the temporal window that attackers could exploit. Organizations should prioritize applying these kernel updates to mitigate the risk of exploitation, particularly in environments where DMA capabilities are available and where firmware security is critical. The vulnerability demonstrates the importance of robust validation mechanisms in firmware contexts and highlights the need for careful consideration of temporal consistency in security-sensitive code paths.
This vulnerability aligns with several cybersecurity frameworks and threat models, including the Common Weakness Enumeration (CWE) classification for improper synchronization in concurrent programming contexts, specifically CWE-367 which addresses Time-of-Check to Time-of-Use (TOCTOU) flaws. From an ATT&CK framework perspective, this vulnerability maps to techniques involving firmware manipulation and privilege escalation through memory corruption, potentially enabling access to T1059 (Command and Scripting Interpreter) and T1542 (Pre-OS Boot) techniques. The issue also relates to broader firmware security concerns such as T1543 (Create or Modify System Process) and T1068 (Exploitation for Privilege Escalation) when considering the potential for attackers to establish persistent access through firmware compromise. The vulnerability underscores the critical need for comprehensive firmware security testing and the implementation of robust temporal consistency checks in privileged firmware code paths to prevent similar issues from arising in other firmware components.