CVE-2023-24535 - Diving into the Panic Caused by Parsing Invalid Messages

Summary: In this post, we will delve into the vulnerability CVE-2023-24535 where parsing certain invalid text-format messages can panic a system. We'll analyse the cause, provide code snippets and explore possible exploits.

Introduction

There is a vulnerability in some systems referred to as CVE-2023-24535, where parsing specific invalid messages can cause a panic. The panic is triggered when a text-format message containing a certain format of a potential number is encountered by the parsing function. In this post, we will dive into the details of this issue, analyze its impact and ways to exploit this vulnerability.

The Cause

The issue is caused by a particular structure in text-format messages. Specifically, when the message contains a number formatted as:

And no further input is present

This leads to a condition where the parsing function cannot handle the message, ultimately causing a panic.

Here's a simple example illustrating the issue

package main

import (
    "fmt"
    "strconv"
)

func main() {
    invalidMessage := "-    "
    number, err := strconv.Atoi(invalidMessage)

    if err != nil {
        fmt.Println("Error while parsing the message:")
        fmt.Println(err)
    } else {
        fmt.Println("Parsed number:", number)
    }
}

In this example, the 'invalidMessage' string contains the specific format that causes the panic. When the strconv.Atoi() function tries to parse this message, it results in an error, which we can handle and display.

However, in some unsecured systems, the same kind of parsing error can lead to a panic.

Exploit Details and Techniques

To exploit this vulnerability, an attacker simply needs to craft a text-format message that conforms to the problematic format we've described above. The attacker can then send this message to the target system to trigger the panic.

There are various methods that an attacker can use to send the invalid message to the target system, such as:

1. Crafting a specific HTTP request with the message included in the URL, query parameters, or the POST payload, if the vulnerable server expects such message formats.
2. Sending the crafted message through messaging systems like email, web forums, or chat platforms, where the target application might attempt to parse messages.
3. Injecting the crafted message during file upload, if the application processes and parses the text content of the uploaded files.

However, it's essential to note that the impact of the CVE-2023-24535 vulnerability can vary depending on the specifics of the target system and its implementation.

The following links provide further information about the vulnerability and related research

- CVE-2023-24535 Official Description
- Related Research Paper - Parsing Perils

Conclusion

The CVE-2023-24535 vulnerability presents a risk to unsecured systems that parse particular text-format messages. The panic caused by this issue can lead to denial of service, crash, or other unforeseen consequences.

While exploiting this vulnerability might be relatively simple, it's crucial to ensure that applications properly handle incoming messages and check for potential invalid formats. Developers should be aware of this issue and take appropriate measures to secure their systems against text-format message parsing vulnerabilities.

Timeline

Published on: 06/08/2023 21:15:00 UTC
Last modified on: 06/15/2023 19:01:00 UTC