GeForce’s graphics cards: Nvidia backdoor enables BIOS modifications

With two new flash tools, the BIOS versions of current GeForce graphics cards can be overwritten – even in the RTX 4000 models.

Two hobbyists have managed to do what Nvidia has been trying to prevent for years: They have designed tools that allow modified BIOS versions to be flashed onto current GeForce graphics cards. Since the GTX-900 generation (Maxwell), this was only possible to a limited extent because the GPUs have since matched the IDs and only accept signed firmwares. The error message “board ID mismatch” appears in case of deviations. AMD also prohibits BIOS modifications for its Radeon graphics cards.

“kefi” now offers the tool nvflashk, “Veii” (omg)vflash. Both are based on the old nvflash tool, but bypass Nvidia’s lock on new graphics cards with updates. “kefi” has, according to its own information, found a backdoor that Nvidia itself has built in and is supposed to allow deviating IDs.

Modifications are of course done at the user’s own risk and void the warranty. There are no security checks during the flash process. Techpowerup checked both tools for malware, but found nothing.

Firmware vulnerability

It is questionable why such a backdoor even exists. Nvidia controls the keys and can simply sign firmwares. Corresponding means are usually also given to partner graphics card manufacturers.

Furthermore, it is a security hole that becomes relevant when several people have physical access to a system. This can be the case for workstations with GeForce graphics cards, for example. It is not known whether professional GPUs also have the backdoor.

At the end of 2018, Intel once screwed up the firmware signing in its NUC mini PCs. The vulnerability CVE-2018-12176 was classified as high-risk at the time with a score of 8.2.

More power

Meanwhile, hobbyists can use the gap to install modified BIOS versions even on current graphics cards like the GeForce RTX 4090. Thus, the power limit can be increased, the fan curve can be changed directly in the BIOS, or the GPU voltage can be increased to squeeze the last percent of clock frequency out of the graphics chip.

Meanwhile, Nvidia can introduce a BIOS flash lock for newly produced graphics cards at any time. Corresponding updates were already available earlier against Nvflash, which was able to bypass the mismatch message for RTX 2000 graphics cards in the meantime.

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