The Common Vulnerabilities and Exposures (CVE) project assigned the code CVE-2022-20454 to a security flaw discovered in the fdt.c file of the Android operating system. This vulnerability could potentially allow an attacker to achieve a local escalation of privilege by exploiting an integer overflow issue in the fdt_next_tag function. The issue affects multiple Android versions, including Android 10, 11, 12, 12L, and 13.

In this long-read post, we will analyze the vulnerability, review the affected code, and discuss the possible impact of this vulnerability on the security of Android devices. We will also explore potential mitigation strategies to protect against this exploit.

Code Snippet & Vulnerability Details

The vulnerability lies in the fdt_next_tag function defined in the fdt.c file. The function is responsible for handling operations related to flattened device trees (FDT). An integer overflow could occur in this function, potentially allowing an attacker to execute an out of bounds write, leading to a local escalation of privilege. To better understand the problem, let's analyze the code snippet below:

uint32_t fdt_next_tag(const void *fdt, uint32_t offset,
                      uint32_t *nextoffset)
    const uint32_t *p = fdt_offset_ptr_(fdt, offset, sizeof(uint32_t));
    uint32_t tag;

    if (!p)
        return FDT_END;

    tag = fdt32_to_cpu(*p);
    offset += FDT_TAGSIZE;
    *nextoffset = fdt_next_offset_(fdt, tag, offset);

    return tag;

In this code snippet, the fdt_next_tag function takes an offset of the current tag as input and processes it to find the next tag in the flattened device tree. The problematic part is in the following line:

*nextoffset = fdt_next_offset_(fdt, tag, offset);

An integer overflow can occur at this line, leading to the out of bounds write and, ultimately, local privilege escalation. Exploiting this vulnerability would require system execution privileges, meaning that an attacker would need to have access to an affected device.

Original References

The vulnerability was first identified in the Android Open Source Project (AOSP) and assigned the Android-ID A-242096164. Information about this vulnerability can be found in the following references:

- Android Security Bulletin - CVE-2022-20454
- AOSP Issue Tracker - A-242096164
- CVE-2022-20454 - CVE Project

Exploit & Impact

Exploiting this vulnerability requires system execution privileges and doesn't need user interaction. If a malicious actor has access to a device running any of the affected Android versions, they could potentially exploit this issue to perform the following actions:

Gain unauthorized access to sensitive data and resources on the device.

- Perform unauthorized actions, such as changing system settings, executing additional payloads, or intercepting user communications.

Persist malicious code on the device, potentially evading detection and prevention measures.

The severity of this vulnerability is considered high, given the potential impact on users' security and privacy.

Mitigation & Recommendations

To protect against exploitation, it is crucial to apply patches and updates to affected Android devices as soon as they become available. Manufacturers and developers should monitor Android security bulletins and implement security updates promptly.

Implement multi-factor authentication (MFA) to reduce the risk of unauthorized access.

In conclusion, the CVE-2022-20454 vulnerability poses a significant risk to the security and privacy of Android device users. By understanding the technical details, applying patches, and following best practices, organizations and individuals can mitigate the potential impact and protect their devices from exploitation.


Published on: 11/08/2022 22:15:00 UTC
Last modified on: 11/09/2022 16:31:00 UTC