What’s Vulnerable › Vulnerabilities

CVE-2021-23384: Open Redirect

• Severity: medium (CVSS 5.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-05-17 · updated 2026-06-17
• Weakness: CWE-601

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.

Affected products

• koa-remove-trailing-slashes: before 2.0.2 — fixed in 2.0.2

How to fix

Upgrade to a fixed version: koa-remove-trailing-slashes 2.0.2. Check the vendor advisory for mitigations.

References

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

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