{"cve":"CVE-2021-21328","nvd":{"published":"2021-02-26T02:15:12.713","modified":"2026-06-17T03:35:18.397","status":"Modified","description":"Vapor is a web framework for Swift. In Vapor before version 4.40.1, there is a DoS attack against anyone who Bootstraps a metrics backend for their Vapor app. The following is the attack vector: 1. send unlimited requests against a vapor instance with different paths. this will create unlimited counters and timers, which will eventually drain the system. 2. downstream services might suffer from this attack as well by being spammed with error paths. This has been patched in 4.40.1. The `DefaultResponder` will rewrite any undefined route paths for to `vapor_route_undefined` to avoid unlimited counters.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3},"cwes":["CWE-400"],"references":["https://github.com/vapor/vapor/commit/e3aa712508db2854ac0ab905696c65fd88fa7e23","https://github.com/vapor/vapor/releases/tag/4.40.1","https://github.com/vapor/vapor/security/advisories/GHSA-gcj9-jj38-hwmc","https://vapor.codes/","https://github.com/vapor/vapor/commit/e3aa712508db2854ac0ab905696c65fd88fa7e23"],"products":["vapor_project:vapor"],"source":"nvd","synced_at":"2026-10-19T21:15:50.279857260+00:00"},"epss":{"cve":"CVE-2021-21328","score":0.01837,"percentile":0.78952,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}