CVE-2022-23121: Remote Code Execution Vulnerability in Netatalk’s Parse_Entries Function

CVE-2022-23121 is a critical vulnerability that potentially allows remote attackers to execute arbitrary code on the affected installations of Netatalk. It is noteworthy to mention that no authentication is required to exploit this security flaw. This vulnerability arises due to the absence of proper error handling while parsing AppleDouble entries in the parse_entries function. An attacker can leverage this weakness to execute code with root-level privileges. This vulnerability was previously indexed as ZDI-CAN-15819.

Vulnerability Analysis

Netatalk is an open-source implementation of the Apple Filing Protocol (AFP) that enables UNIX-like systems to serve as file servers for macOS clients. The affected Netatalk versions contain a flawed implementation of the parse_entries function that could be exploited by a malicious user.

The main issue arises from the lack of proper error handling when parsing AppleDouble entries, which leads to memory corruption and potentially allows arbitrary code execution in the context of the root user. Here is the problematic code snippet:

static int parse_entries(struct vol *vol, const char *path, ...){
    ...
    while (rbuf < entries_end) {
        struct extmap *em = NULL;
        uint32_t entry_id = be32dec(rbuf); /* entry ID */
        uint32_t ofs = be32dec(rbuf + 4);  /* offset */
        uint32_t len = be32dec(rbuf + 8);  /* length */
        ...
        if (entry_id <= EXTM_INV) {
            continue;
        }
        ...
        while (em) {
            if (em->read(vol, path, entry_id, &buf, &len) == ) {
                ...
            }
        }
    }
}

Exploit Details

An attacker can exploit this vulnerability by crafting a malicious AppleDouble request and sending it to the vulnerable Netatalk server. The crafted request should include a specially formatted AppleDouble entry that triggers the vulnerability, causing memory corruption and allowing remote code execution in the context of the root user.

To fully understand the implications and the technical details of this vulnerability, it's essential to refer to the original references provided by the researchers who discovered and reported the flaw:

1. CVE-2022-23121: Netatalk Remote Code Execution Vulnerability
2. ZDI-CAN-15819

Mitigation

To mitigate the risk associated with CVE-2022-23121, users and administrators are encouraged to apply the appropriate patches provided by the vendor as soon as possible. If patches are not available, it is advised to limit access to the Netatalk server and closely monitor network traffic for any malicious activities.

Conclusion

CVE-2022-23121 poses a significant threat to affected Netatalk installations due to its potential for enabling remote code execution without authentication requirements. As with any vulnerability, it's crucial to stay up-to-date on patches and follow best practices for securing your environment. Timely patching and vigilant network monitoring can help mitigate the risk associated with this vulnerability and minimize potential damage from an exploit.

Timeline

Published on: 03/28/2023 19:15:00 UTC
Last modified on: 04/03/2023 18:16:00 UTC