Open redirect in Slashify

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2021-3189: 0.53% estimated exploitation activity in the next 30 days; percentile 44.60 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

The package is an Express middleware that normalises routes by stripping any final slash, redirecting, for example, bookings/latest/ to bookings/latest. However, it does not validate the path it redirects to in any way. In particular, if the path starts with two slashes (or two backslashes, or a slash and a backslash, etc.) it may redirect to a different domain. Consider the example from the docs. Assume we have run it and started a server on localhost:3000, then visiting localhost:3000///github.com/ redirects you to https://github.com. Recommendation This vulnerability is currently un-patched in the slashify package so there is no known safe version of this package. Discontinuing use of slashify is recommended.

Published by the source

5 Feb 2021, 20:43 UTC

Last modified by the source

8 Nov 2023, 04:05 UTC

Source last checked

26 Oct 2026, 12:20 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-f4hq-453j-p95f

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-f4hq-453j-p95f

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# Patch Next advisory brief: CVE-2021-3189

Advisory: Open redirect in Slashify
IDs: CVE-2021-3189, GHSA-f4hq-453j-p95f
Record: https://patchnext.com/advisories/cve-2021-3189 (revision 2, source checked 26 Oct 2026, 12:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm slashify: affected <= 1.0.0

## Suggested inspection (read-only)
- `npm ls slashify --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on slashify.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-f4hq-453j-p95f (OSV record GHSA-f4hq-453j-p95f lists affected ranges: npm slashify >=0 <=1.0.0)
- Verified: https://github.com/advisories/GHSA-f4hq-453j-p95f (GitHub-reviewed advisory GHSA-f4hq-453j-p95f lists affected ranges: npm slashify >=0 <=1.0.0)

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