Prototype Pollution in Shepherdwind Velocity.js
CVE-2026-44966
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.
Vulnerability class: Prototype Pollution
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:L.
EPSS exploit prediction
EPSS: 0.005 (44.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 45th percentile — 44.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000
Affected products
- Shepherdwind Velocity.js — versions <= 2.1.5
Weakness classification (CWE)
References
- github.com/shepherdwind/velocity.js/security/advisories/GHSA-j658-c2gf-x6pq (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-44966?
- CVE-2026-44966 is a high-severity vulnerability in Shepherdwind Velocity.js, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 8.3/10. Published 2026-05-26.
- How severe is CVE-2026-44966?
- High severity. CVSS v3 base score is 8.3 out of 10.