CVE-2021-21328

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.

• CWE-400

• https://github.com/vapor/vapor/commit/e3aa712508db2854ac0ab905696c65fd88fa7e23Patch, Third Party Advisory
• https://github.com/vapor/vapor/releases/tag/4.40.1Release Notes, Third Party Advisory
• https://github.com/vapor/vapor/security/advisories/GHSA-gcj9-jj38-hwmcThird Party Advisory
• https://vapor.codes/Product
• https://github.com/vapor/vapor/commit/e3aa712508db2854ac0ab905696c65fd88fa7e23Patch, Third Party Advisory
• https://github.com/vapor/vapor/releases/tag/4.40.1Release Notes, Third Party Advisory
• https://github.com/vapor/vapor/security/advisories/GHSA-gcj9-jj38-hwmcThird Party Advisory
• https://vapor.codes/Product

Published

Feb 26, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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