In this long-read post, we'll be discussing CVE-2024-21539, a vulnerability discovered in some versions of the package @eslint/plugin-kit. This security issue essentially affects all versions of the package before .2.3, making them vulnerable to a Regular Expression Denial of Service (ReDoS) attack. An attacker with knowledge of this vulnerability can exploit it to increase the CPU usage and crash the target program, causing a denial of service.
In this detailed analysis, we'll lay out the specific exploit details, including a code snippet showcasing the vulnerability and how an attacker might exploit it. Additionally, we will highlight the original references to this vulnerability, and discuss the steps needed to resolve it.
Regular Expression Denial of Service (ReDoS) Vulnerability
A ReDoS attack is a type of vulnerability where an attacker exploits a flaw in the regular expression processing of software to cause performance issues or completely crash the program. In the case of CVE-2024-21539, the vulnerability is due to improper input sanitization, allowing the attacker to craft a specially designed input that would trigger the ReDoS attack.
Code Snippet
The following code snippet represents the vulnerable regular expression pattern in @eslint/plugin-kit:
'''
// Vulnerable code in @eslint/plugin-kit
const regex = /^([a-z][a-zA-Z-9]*(-[a-zA-Z-9]+)*)+$/;
const userInput = "abcdefghijklmnopqrstuv123456789-";
if (regex.test(userInput)) {
console.log("Input passes the validation.");
} else {
console.log("Invalid input.");
}
'''
The regex variable represents a regular expression pattern that is used to validate user input. The improper input sanitization allows an attacker to feed a specially crafted input string that, when tested against the regex pattern, causes exponential processing time in the validation, leading to CPU usage spikes and potentially crashing the program.
Exploiting the Vulnerability
An attacker taking advantage of the CVE-2024-21539 vulnerability can craft an input string that triggers the ReDoS vulnerability, for example:
'''
const maliciousInput = "abcdefghijklmnopqrstuv123456789-".repeat(10000);
if (regex.test(maliciousInput)) {
console.log("Input passes the validation.");
} else {
console.log("Invalid input.");
}
'''
In this code snippet, the attacker repeats the maliciousInput string 10,000 times, which, when tested against the regex pattern, causes excessive processing time that can crash the program, leading to a denial of service.
Original References
1. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-21539
2. https://github.com/eslint/eslint-plugin-kit/issues/42
3. https://github.com/eslint/eslint-plugin-kit/pull/43
Resolution
To resolve this vulnerability in your application, you should update your @eslint/plugin-kit package to version .2.3 or later. This can be done by modifying your package.json file and running an update:
'''
// Update package.json to include the fixed version
{
"dependencies": {
"@eslint/plugin-kit": "^.2.3"
}
}
// Update your packages
npm update
'''
By updating to version .2.3 or later, you can ensure that your application is no longer vulnerable to CVE-2024-21539 and the associated ReDoS attack, protecting your program from potential exploitation that leads to increased CPU usage and crashes.
Timeline
Published on: 11/19/2024 05:15:16 UTC
Last modified on: 11/19/2024 21:57:32 UTC