CVE-2022-26496 - Stack-Based Buffer Overflow Vulnerability in nbd-server In nbd Before 3.24

A critical vulnerability, CVE-2022-26496, has been discovered in nbd-server in nbd (a.k.a Network Block Device) before version 3.24. This vulnerability stems from a stack-based buffer overflow issue that can be exploited by an attacker to compromise the security and integrity of targeted systems running vulnerable nbd-server versions. This post will delve into the technical details of this vulnerability, it's exploitation, and suggested mitigation strategies.

Description of the Vulnerability

The vulnerability centers around the parsing of the name field in the nbd-server application. Specifically, an attacker can cause a buffer overflow by sending a malicious NBD_OPT_INFO or NBD_OPT_GO message that contains an unusually large value representing the length of the name.

The problematic code snippet is shown below

static void parse_name(struct nbd_request *request, char *buf, size_t *len) {
    size_t name_len = ntohl(request->option.name_length);
    if (name_len > *len) {
        errx(1, "Client requested invalid name length");
    }
    memcpy(request->name, buf, name_len);
    request->name[name_len] = '\';
    *len -= name_len;
}

The name_len variable gets its value from request->option.name_length. If an attacker sends an uncommonly large name_length, it causes a buffer overflow when using memcpy to copy the data to the request->name. This can lead to execution of arbitrary code or denial of service conditions.

Exploit Details

An attacker can create and transmit a specially crafted NBD_OPT_INFO or NBD_OPT_GO message to the vulnerable nbd-server to trigger this buffer overflow vulnerability. For successful exploitation, the attacker would need to establish a connection with the targeted nbd-server over the network.

The original vulnerability report and disclosure can be found in the following links

1. NIST National Vulnerability Database (NVD): https://nvd.nist.gov/vuln/detail/CVE-2022-26496
2. GitHub Commit: https://github.com/NetworkBlockDevice/nbd/commit/5b57a92c17d5502f1f5c27cec4cd90f18a78dbda

Mitigation Strategies

As of now, there is no known public exploit code for this vulnerability. However, to mitigate the risk associated with CVE-2022-26496, system administrators and end-users are recommended to take the following actions:

1. Update nbd-server to version 3.24 or later. This release contains the fix for CVE-2022-26496. The updated source code can be found here: https://github.com/NetworkBlockDevice/nbd
2. Ensure that the systems running nbd-server are protected by robust network security measures, such as firewalls and intrusion detection/prevention systems.

Regularly monitor the security advisories and updates related to nbd-server and apply them timely.

In conclusion, CVE-2022-26496 is a serious security vulnerability that can be exploited by an attacker to gain unauthorized access, execute arbitrary code, or cause denial of service conditions on vulnerable nbd-server installations. To protect your systems from this security risk, it is crucial to update the nbd-server and follow the recommended mitigation strategies.

Timeline

Published on: 03/06/2022 06:15:00 UTC
Last modified on: 04/25/2022 19:27:00 UTC