In early 2022, a security issue, CVE-2022-30790, was identified in Das U-Boot, the popular open-source bootloader used in many embedded devices. This vulnerability involves a buffer overflow in version 2022.01 and is *distinct* from the earlier issue CVE-2022-30552. In this article, we'll break down what CVE-2022-30790 is, how it works, and even walk through example code demonstrating the problem. We’ll close with authoritative references and some direct tips for mitigation.

What is Das U-Boot?

First, a quick refresher: U-Boot is a bootloader program that's responsible for starting up embedded systems like routers, set-top boxes, and even some mobile devices. Because it's one of the first things to run when a device turns on, vulnerabilities in U-Boot can have serious consequences.

What is CVE-2022-30790?

CVE-2022-30790 is a buffer overflow vulnerability found in Das U-Boot v2022.01. It was disclosed in June 2022. The issue is *not* the same as CVE-2022-30552, which affects different code paths in U-Boot.

Versions Affected: 2022.01 (possibly others)

- CVE: CVE-2022-30790

Where’s the Problem?

The vulnerable code is in U-Boot's handling of certain device data, specifically, in code that doesn't properly check the length of an input string before copying it into a fixed-size buffer.

Here is a simplified version of what such an issue might look like (not the exact code, but representative):

#define BUFFER_SIZE 64

void vulnerable_function(const char *input) {
    char buffer[BUFFER_SIZE];
    strcpy(buffer, input);  // unsafe: no length check!
    // ... do something with buffer ...
}

If an attacker manages to provide an input string longer than BUFFER_SIZE, the extra data will overwrite adjacent memory, which can lead to arbitrary code execution.

In U-Boot 2022.01, this kind of vulnerability exists in code that parses device descriptors and configuration data. A specially crafted device or corrupted input can overflow the buffer.

Here's what an attack might look like, conceptually

1. Malicious input (like a too-long device name) is provided (either via network, USB, or through a flashed image).

Let’s say there's a buffer that takes a string from an external storage descriptor

void process_device_info(const char *dev_name) {
    char name_buf[32];
    // Unsafe copy!
    sprintf(name_buf, "%s", dev_name);
    // ... further processing ...
}

An attacker could craft dev_name as a string longer than 32 bytes, causing name_buf to overflow. Exploiting this in practice would require knowledge of the memory layout, but it’s a classic and severe bug pattern.

Exploit Scenario

Imagine an embedded device that reads its configuration at boot from a removable card. If someone can place a configuration file or device which injects an overly long string into U-Boot’s code (e.g., during boot time USB device enumeration), this buffer overflow could be triggered, possibly injecting code that runs with full firmware privileges.

On devices where U-Boot handles network input or offers update services, remote exploitation could be possible.

References & Further Reading

- Official CVE Entry - CVE-2022-30790 (NIST)
- Upstream U-Boot Project
- U-Boot Security Advisory (Das U-Boot Mailing List) *(if link is broken, search public archives for CVE discussion)*
- About Buffer Overflows (OWASP)

Update U-Boot to the latest version. Patches are available in newer releases.

- Do not use strcpy, sprintf, or other unsafe string functions. Use safer versions like strncpy and snprintf that require explicit buffer sizes.

Summary

CVE-2022-30790 poses a real risk to embedded devices using unpatched versions of U-Boot. It’s a great case study of why even simple C programming mistakes (like forgetting to check buffer sizes) can lead to vulnerabilities that attackers may use to take over devices. By understanding the details and updating your bootloader, you can stay ahead of these serious threats.

*For developers and system integrators, always follow best secure coding practices—and consider the bootloader as critical infrastructure!*

Timeline

Published on: 06/08/2022 13:15:00 UTC
Last modified on: 06/16/2022 13:28:00 UTC