shepherdwind velocity.js up to 2.1.5 prototype pollution

Summaryinfo

A vulnerability labeled as critical has been found in shepherdwind velocity.js up to 2.1.5. Affected by this issue is some unknown functionality. Executing a manipulation can lead to prototype pollution. This vulnerability is tracked as CVE-2026-44966. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in shepherdwind velocity.js up to 2.1.5 and classified as critical. This vulnerability affects an unknown part. The manipulation with an unknown input leads to a prototype pollution vulnerability. The CWE definition for the vulnerability is CWE-1321. The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Velocity.js is a JavaScript implementation of the Apache Velocity template engine. In 2.1.5 and earlier, a prototype pollution vulnerability was discovered in velocityjs. This issue occurs during the processing of #set directives in Velocity templates. If an application renders a template controlled by an attacker, it is possible to modify Object.prototype, potentially leading to Denial of Service (DoS) or Remote Code Execution (RCE) depending on the server environment.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-44966 since 05/08/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 05/27/2026). The MITRE ATT&CK project declares the attack technique as T1059.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• JavaScript Library

Vendor

• shepherdwind

Name

• velocity.js

Version

• 2.1.0
• 2.1.1
• 2.1.2
• 2.1.3
• 2.1.4
• 2.1.5

Website

• Product: https://github.com/shepherdwind/velocity.js/

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