BMC Firmware Vulnerabilities Allow Attackers to Bypass Signature Verification Features

Critical vulnerabilities discovered in Supermicro Baseboard Management Controller (BMC) firmware have exposed a troubling pattern where inadequate security fixes create new attack vectors, allowing sophisticated adversaries to bypass signature verification mechanisms and maintain persistent control over enterprise server infrastructure.

These flaws, affecting multiple generations of Supermicro motherboards, demonstrate how design weaknesses in firmware validation processes can undermine the fundamental security assumptions of server hardware.

The vulnerabilities emerged following an investigation into supposedly fixed security issues, revealing that vendor patches implemented in January 2025 were insufficient to address the underlying authentication flaws.

The original vulnerability, CVE-2024-10237, was discovered by NVIDIA’s Offensive Security Research Team and involved fundamental flaws in BMC firmware image authentication design that could allow attackers with administrative access to upload malicious firmware updates.

Binarly analysts identified a bypass technique for the vendor’s CVE-2024-10237 fix, resulting in the assignment of CVE-2025-7937.

During their extended analysis of different Supermicro products, researchers discovered a similar vulnerability employing distinct exploitation techniques, assigned CVE-2025-6198.

The exploitation of this second vulnerability revealed capabilities extending beyond mere firmware updates, enabling attackers to bypass the BMC Root of Trust (RoT) security feature entirely.

The attack vectors leverage design flaws in the three-step firmware validation process used across Supermicro’s BMC implementations.

Initially, the system retrieves a public key from the BMC SPI flash chip forming part of the currently running firmware, while extracting cryptographic signature values from uploaded image blobs using RSA-4096 verification.

The process then analyzes embedded tables representing different firmware regions, calculating SHA-512 hash digests of signed regions before verifying signatures against calculated digests.

These vulnerabilities grant attackers complete persistent control over both BMC systems and main server operating systems, representing a critical escalation pathway that compromises fundamental hardware security assumptions in enterprise environments.

Exploitation Mechanisms and Signature Bypass Techniques

The bypass techniques exploit fundamental weaknesses in how firmware validation logic processes region tables embedded within uploaded images.

For CVE-2025-7937, attackers circumvent the supposed fixes by introducing custom fwmap tables before original ones, containing single elements that encompass all signed regions concatenated together.

The exploit leverages the fact that fwmap tables are located in memory by signature rather than fixed positions, allowing manipulation of the validation sequence.

In the X12STW-F firmware version 01.06.17, the original validation process defines six distinct regions with specific offsets and signing requirements.

The bypass technique creates a consolidated entry at offset 0x100000 with size 0x2b32c00 marked as signed boot content, effectively wrapping all legitimate signed regions into a single validated block while inserting malicious content in the bootloader space.

For CVE-2025-6198, the exploitation technique targets the auth_bmc_sig function within the OP-TEE environment, manipulating the sig_table section located at offset 0x100000.

This alternative validation method processes region information differently, storing offsets in the first four bytes and custom-transformed size values in remaining bytes.

By modifying kernel regions and updating corresponding sig_table entries, attackers maintain signature validity while executing arbitrary code during BMC boot processes.

The successful exploitation of these techniques results in persistent arbitrary code execution capabilities, with modified kernel images bypassing authentication mechanisms during boot sequences.

Binarly researchers demonstrated successful validation and flashing of modified images through UART debugging interfaces, confirming that customized kernels execute without triggering security mechanisms, effectively compromising the entire BMC security model.

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