Recently, a significant security vulnerability, CVE-2023-38471, was identified in the widely-used Avahi software. This vulnerability exposes an issue within the dbus_set_host_name() function, leaving systems that utilize this software at risk. In this post, we will delve into the details of this vulnerability, study the relevant code snippets, and discuss the potential exploit implications.


For those unfamiliar with the software, Avahi is an open-source implementation of the Zeroconf networking protocol suite. It is widely used in UNIX systems for service discovery on local networks, enabling users to find and utilize various network resources with ease. More information about this software package can be found on the official Avahi website:

Vulnerability Details - CVE-2023-38471

The vulnerability lies within the dbus_set_host_name() function in the Avahi software. A reachable assertion leads to an issue where an attacker, using a specially crafted DBUS message, could potentially exploit the vulnerability, causing denial of service (DoS) or other impacts on the targeted system. The affected software versions are .8 and earlier. The Avahi maintainers have acknowledged this issue and assigned CVE-2023-38471 as an identifier.

Affected Code Snippet

To better understand the vulnerability, we can examine the affected code snippet in the dbus-internal.c file, found within the Avahi source code:

// dbus-internal.c
static void dbus_set_host_name(AvahiServer *s, DBusMessage *message) {
    dbus_int32_t ret;
    char *n;
    DBusError error;


    // ... unrelated code


    if (!dbus_message_get_args(message, &error, DBUS_TYPE_STRING, &n, DBUS_TYPE_INVALID))

    if (strlen(n) >= AVAHI_DOMAIN_NAME_MAX) {
        dbus_set_error_const(&error, DBUS_ERROR_INVALID_ARGS, "Invalid hostname");
    // ... unrelated code

In the code snippet above, the vulnerability is linked to the absence of proper validation. The function dbus_message_get_args() gets the desired hostname provided by the user. However, it does not sufficiently validate the length of the given hostname (n). Consequently, an attacker can submit a specially crafted, oversized hostname that triggers the reachable assertion, leading to a potential exploit.

Note that the code snippet above represents an older version of Avahi, where the vulnerability still exists. As of now, there is no official patch that addresses this specific issue. However, the Avahi team is likely to address this vulnerability in a future update.

Exploit Implications

As mentioned earlier, this vulnerability opens up the possibility of an attacker utilizing a specifically crafted DBUS message to trigger the reachable assertion. In turn, this can result in a denial of service (DoS) or other impacts. The attacker could cause the Avahi service to crash or execute malicious code with the same privileges as the running Avahi service.


In summary, CVE-2023-38471 represents a substantial security vulnerability in the well-established Avahi software package. Users and administrators are encouraged to keep an eye out for any official updates or patches from the Avahi team that address this issue. As with any software vulnerability, it is crucial to take this alert seriously and respond promptly to minimize the risk of potential exploits.

Original References

1. Avahi website:
2. Avahi GitHub repository (where the vulnerability was identified):
3. CVE-2023-38471:

Stay tuned to our blog for further updates on this and other security vulnerabilities.


Published on: 11/02/2023 15:15:08 UTC
Last modified on: 11/09/2023 19:58:27 UTC