CVE-2022-35897 is a stack buffer overflow vulnerability found in InsydeH2O firmware versions with kernel 5.0 through 5.5. This vulnerability arises when an attacker modifies specific UEFI variables—namely SecureBootEnforce, SecureBoot, and RestoreBootSettings. These variables are typically locked and read-only at the operating system level, preventing unauthorized modification. However, if an attacker can directly modify the SPI flash memory (which stores the firmware and UEFI variables), they can change at least two of these variables. Doing so triggers a stack buffer overflow condition within the UEFI firmware, enabling arbitrary code execution at the firmware level. This is a critical security concern because firmware-level compromise can bypass operating system security controls, persist through OS reinstalls, and potentially control the entire system from boot. The vulnerability requires physical or privileged access to the SPI flash memory to modify these variables, as normal OS-level protections prevent such changes. The CVSS 3.1 base score is 6.8 (medium severity), reflecting the requirement for physical or privileged access (attack vector: physical), but with high impact on confidentiality, integrity, and availability if exploited. No known public exploits have been reported in the wild to date. The vulnerability is classified under CWE-787 (Out-of-bounds Write), indicating a classic buffer overflow issue. No patches or vendor advisories are currently linked, suggesting that mitigation may rely on hardware or firmware updates from device manufacturers or secure SPI flash protections. Given the nature of the vulnerability, exploitation is non-trivial and likely limited to targeted attacks where the attacker has physical access or has already compromised the system to a high degree.

For European organizations, the impact of this vulnerability could be significant in environments where devices use InsydeH2O firmware versions with kernel 5.0 through 5.5, especially in sectors requiring high security such as government, defense, critical infrastructure, and finance. A successful exploit could allow attackers to execute arbitrary code at the firmware level, leading to persistent and stealthy compromise that is difficult to detect and remediate. This could result in theft of sensitive data, sabotage of system integrity, or disruption of availability. Since the attack requires modification of SPI flash memory, it is more likely to be leveraged in targeted attacks involving insider threats, supply chain compromises, or physical access scenarios. European organizations with strict regulatory requirements around data protection and system integrity (e.g., GDPR, NIS Directive) could face compliance risks if such firmware-level compromises occur. Additionally, the ability to disable or manipulate Secure Boot settings undermines a critical security control designed to prevent unauthorized code execution during system startup, increasing the risk of persistent malware infections or rootkits. The lack of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time. Organizations relying on devices with affected firmware should consider this vulnerability a serious risk to their endpoint security posture.

1. Inventory and identify all devices using InsydeH2O firmware with kernel versions 5.0 through 5.5 within the organization. 2. Engage with device manufacturers or vendors to obtain firmware updates or patches addressing this vulnerability; if unavailable, request guidance on secure firmware configurations. 3. Implement hardware-level protections to restrict unauthorized SPI flash memory access, such as enabling SPI flash write protection via hardware jumpers or BIOS settings where available. 4. Enforce strict physical security controls to prevent unauthorized physical access to devices, including secure storage, surveillance, and access logging. 5. Monitor firmware integrity using trusted platform module (TPM)-based attestation or firmware integrity verification tools to detect unauthorized modifications. 6. Harden endpoint security by restricting administrative privileges and employing endpoint detection and response (EDR) solutions capable of detecting anomalous firmware or boot-level behavior. 7. Incorporate firmware security checks into regular vulnerability assessments and penetration testing to identify potential exploitation attempts. 8. Educate IT and security teams about the risks of firmware-level attacks and the importance of protecting firmware variables and SPI flash memory. These measures go beyond generic patching advice by focusing on physical security, hardware protections, and firmware integrity monitoring, which are critical given the nature of this vulnerability.