A newly discovered vulnerability, identified as CVE-2022-30065, exposes a use-after-free issue in Busybox 1.35-x's awk applet. The vulnerability could lead to denial of service (DoS) and, under certain conditions, even potentially allow for remote code execution. This vulnerability arises from a flaw in the copyvar function while processing a crafted awk pattern.

In this long-read post, we'll discuss the details surrounding CVE-2022-30065, including a code snippet highlighting the vulnerable function, links to original references, and a brief explanation of the potential exploit scenario.

Vulnerable Code Snippet

The vulnerability exists within the copyvar function located in the Busybox awk applet source code. The code snippet below highlights the problematic area:

// busybox-1.35./shell/ash.c
...
void copyvar(dest, src) {
    ...
    if (!(src->type & (VARCONST|VAREUNSET))) {
        if (dest->type & VAREUNSET) {
            dest->text = str_save(src->text, funcname);
        } else {
            dest->text = ckrealloc(dest->text, 
                strlen(src->text) +1, funcname);
        }
        ...
    }
    ...
}

When a specially crafted awk pattern is processed, the vulnerability in the copyvar function can cause a use-after-free condition, resulting in denial of service and, potentially, code execution under specific circumstances.

Original References

1. BusyBox's official website: https://busybox.net/
2. NVD (National Vulnerability Database) entry for CVE-2022-30065: https://nvd.nist.gov/vuln/detail/CVE-2022-30065
3. BusyBox 1.35-x's official source code repository: https://git.busybox.net/busybox/

Potential Exploit Details

To exploit this vulnerability, an attacker would first need to craft a malicious awk pattern designed to trigger the use-after-free condition in the copyvar function. By carefully manipulating memory and controlling the details of this vulnerability, an attacker could escalate the impact from a simple denial of service to possibly achieving remote code execution on the target system. However, successful exploitation for code execution would likely be more challenging, as it would require additional steps and a deeper understanding of the target environment.

Mitigation Steps

As of now, there has been no official patch released to address this vulnerability. Users should keep an eye on BusyBox's official channels for updates and patch releases. In the meantime, users can consider the following mitigation measures:

Implement strict input validation and sanitation methods before processing any awk patterns.

3. Monitor and restrict access to systems running Busybox 1.35-x, especially those instances making substantial use of the awk applet.

Conclusion

The CVE-2022-30065 vulnerability exposes a use-after-free condition in Busybox 1.35-x's awk applet, which could lead to denial of service and, under specific conditions, even potential code execution. By understanding the details of this vulnerability and staying informed about patches and mitigation steps, users can work to protect their systems from potential exploitation.

Timeline

Published on: 05/18/2022 15:15:00 UTC
Last modified on: 06/01/2022 14:20:00 UTC