CVE-2026-50720 in T31
Summary
by MITRE • 08/19/2026
The Ingenic T31 SoC boot ROM flash-boot verification path compares only a single 32-bit word of the RSA signature output against a single 32-bit word of the SHA-256 payload digest, rather than compare the full data. This allows an attacker with physical write access to boot media to forge modified SPL (Secondary Program Loader) images that pass secure boot verification without possession of the OEM signing key. Each forgery attempt succeeds with approximately 2/3 probability. This has been validated via reverse engineering, software emulation against vendor-signed images, and end-to-end hardware acceptance of a forged firmware image on a Wyze Video Doorbell v2 (T31X).
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Analysis
by VulDB Data Team • 08/19/2026
The Ingenic T31 System-on-Chip contains a critical flaw in its boot ROM secure boot implementation that fundamentally undermines the integrity guarantees provided by RSA signature verification. The vulnerability resides specifically within the flash-boot verification path, where the hardware is designed to validate the authenticity of firmware images before execution. Instead of performing a complete cryptographic comparison between the decrypted RSA signature and the computed SHA-256 hash of the payload, the implementation only compares a single 32-bit word from each data structure. This truncated validation mechanism creates a severe mathematical weakness that allows an attacker with physical write access to boot media to bypass secure boot protections entirely. The flaw effectively reduces the security boundary from a robust cryptographic proof to a probabilistic guess based on limited byte alignment, rendering the secure boot feature ineffective against determined adversaries possessing hardware-level access.
From a technical perspective, this vulnerability is classified as CWE-347: Improper Verification of Cryptographic Signature. By comparing only one 32-bit word out of what should be a full SHA-256 digest and RSA signature block, the verification process fails to ensure that the entire payload matches the signed content. The probability of success for an attacker forging a valid SPL image is approximately two-thirds per attempt, which is exceptionally high for cryptographic bypasses. This statistical likelihood means that brute-forcing or crafting forged images requires minimal effort compared to breaking standard RSA-2048 or higher encryption schemes. The vulnerability has been validated through rigorous reverse engineering of the boot ROM code and software emulation against vendor-signed images. Furthermore, end-to-end hardware acceptance testing on a Wyze Video Doorbell v2 equipped with the T31X variant confirmed that forged firmware images can be successfully loaded and executed, demonstrating real-world exploitability in consumer IoT devices.
The operational impact of this vulnerability is severe for any device relying on the Ingenic T31 series for secure boot functionality. An attacker who gains physical access to the storage medium containing the bootloader or secondary program loader can inject malicious code that will be accepted by the hardware as legitimate. This allows for persistent root-level compromise, installation of backdoors, and complete control over the device's operating system without detection by standard security mechanisms. Since secure boot is typically the first line of defense in embedded systems, its failure exposes all subsequent layers of security to risk. Attackers can modify firmware updates, intercept data transmission, or use the compromised device as a pivot point for network attacks. The high success rate of forgery attempts makes this vulnerability particularly dangerous in mass-produced IoT devices where physical access might be gained through theft, loss, or targeted hardware hacking campaigns.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. For affected products currently in the field, vendors should issue firmware updates that implement a software-based secure boot verification layer running after the initial ROM check but before full system initialization. This secondary validation can perform the complete SHA-256 comparison to ensure integrity despite the hardware flaw. However, this is only a partial mitigation as it relies on code execution within potentially compromised environments. The most effective solution requires Ingenic and OEMs to release updated boot ROM firmware that corrects the verification logic to compare full signature blocks against full payload digests. Additionally, manufacturers should enforce strict physical security controls for devices using these SoCs, including tamper-evident packaging and secure enclosure designs to deter physical access attempts. Industry standards such as NIST SP 800-193 for Platform Firmware Resiliency guidelines recommend multiple layers of verification; this vulnerability highlights the danger of relying solely on hardware-level checks without redundant software-based integrity validation.