Vulnerability · Published Sep 4, 2026 · Assigned by VulnCheck
CVE-2026-85625sift 17.1.3 Prototype Pollution Remote Code Execution via $where
High 8.1
In plain English
A high-severity prototype pollution in sift.js from crcn. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.7% (higher than 55% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.
Official description
sift (sift.js) 17.1.3 enumerates query keys with for...in, which walks the object prototype chain, and dispatches any matched operator key including $where. The $where operation compiles a string value into a function using new Function unless CSP_ENABLED is set (not set by default). As a result, if a prototype-pollution primitive elsewhere in the process sets Object.prototype.$where to a malicious string, even benign filter calls such as sift({}) execute arbitrary JavaScript. Additionally, passing an untrusted query object containing a string $where directly to sift results in code execution under the default configuration.
Affected products (as reported)
Weakness: CWE-1321 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
References
- GitHub Issue #276 issue-tracking
- https://github.com/crcn/sift.js product
- https://github.com/crcn/sift.js/blob/v17.1.3/src/core.ts technical-description
- VulnCheck Advisory: sift 17.1.3 Prototype Pollution Remote Code Execution via $where third-party-advisory