Prototype pollution in Express - CVE-2024-51999
Published: December 1, 2025
Vulnerability identifier: #VU118878
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2024-51999
CWE-ID: CWE-1321
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to execute arbitrary JavaScript code.
The vulnerability exists due to improper input validation when using the extended query parser in express ('query parser': 'extended'). A remote attacker can pass specially crafted input to the application and perform prototype pollution, which can result in information disclosure or data manipulation.
Affected software
Express
How to mitigate CVE-2024-51999
Install updates from vendor's website.
Express - addressed in versions 4.22.0, 5.1.0