Overly permissive origin policy

Exploitation

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

CVSS

8.6 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N

EPSS

• CVE-2023-49803: 0.28% estimated exploitation activity in the next 30 days; percentile 20.38 (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.

Currently, the middleware operates in a way that if an allowed origin is not provided, it will return an Access-Control-Allow-Origin header with the value of the origin from the request. This behavior completely disables one of the most crucial elements of browsers - the Same Origin Policy (SOP), this could cause a very serious security threat to the users of this middleware. If such behavior is expected, for instance, when middleware is used exclusively for prototypes and not for production applications, it should be heavily emphasized in the documentation along with an indication of the risks associated with such behavior, as many users may not be aware of it.

Published by the source

11 Dec 2023, 21:46 UTC

Last modified by the source

10 Sep 2026, 03:50 UTC

Source last checked

26 Oct 2026, 12:30 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-qxrj-hx23-xp82

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-qxrj-hx23-xp82

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# Patch Next advisory brief: CVE-2023-49803

Advisory: Overly permissive origin policy
IDs: CVE-2023-49803, GHSA-qxrj-hx23-xp82
Record: https://patchnext.com/advisories/cve-2023-49803 (revision 2, source checked 26 Oct 2026, 12:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @koa/cors 5.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @koa/cors: affected < 5.0.0; fixed in 5.0.0

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

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @koa/cors.
- 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-qxrj-hx23-xp82 (OSV record GHSA-qxrj-hx23-xp82 lists affected ranges: npm @koa/cors >=0 <5.0.0 (fixed))
- Verified: https://github.com/advisories/GHSA-qxrj-hx23-xp82 (GitHub-reviewed advisory GHSA-qxrj-hx23-xp82 lists affected ranges: npm @koa/cors >=0 <5.0.0)

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