Winter vulnerable to privilege escalation by authenticated backend users

Exploitation

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

CVSS

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

EPSS

• CVE-2026-27591: 0.69% estimated exploitation activity in the next 30 days; percentile 52.75 (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.

Impact Affected versions of Winter CMS allowed authenticated backend users to escalate their accounts level of access to the system by modifying the roles / permissions assigned to their account through specially crafted requests to the backend while logged in. To actively exploit this security issue, an attacker would need access to the Backend with a user account with any level of access. The Winter CMS maintainers strongly recommend that all Winter CMS sites that have any reliance on the roles & permissions system to update immediately. Security fixes have been backported to all major versions of Winter (1.0, 1.1, and 1.2). Patches Multiple fixes and defence in depth has been applied to prevent current and future privilege escalation attacks at the lowest level possible. This security issue has been fixed as of https://wintercms.com/releases/v1.0.477, https://wintercms.com/releases/v1.1.12, https://wintercms.com/releases/v1.2.12. Workarounds If you cannot upgrade, you may apply…

Published by the source

12 Mar 2026, 14:07 UTC

Last modified by the source

12 Mar 2026, 14:07 UTC

Source last checked

26 Oct 2026, 14:38 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pgpf-m8m4-6cg6

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# Patch Next advisory brief: CVE-2026-27591

Advisory: Winter vulnerable to privilege escalation by authenticated backend users
IDs: CVE-2026-27591, GHSA-pgpf-m8m4-6cg6
Record: https://patchnext.com/advisories/cve-2026-27591 (revision 1, source checked 26 Oct 2026, 14:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: winter/wn-backend-module 1.2.12, 1.1.12, 1.0.477. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist winter/wn-backend-module: affected >= 1.2.0, < 1.2.12; >= 1.1.0, < 1.1.12; < 1.0.477; fixed in 1.2.12, 1.1.12, 1.0.477

## Suggested inspection (read-only)
- Packagist winter/wn-backend-module: check the installed version with your package manager.

## 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 winter/wn-backend-module.
- 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://github.com/advisories/GHSA-pgpf-m8m4-6cg6 (GitHub-reviewed advisory GHSA-pgpf-m8m4-6cg6 lists affected ranges: Packagist winter/wn-backend-module >=1.2.0 =1.1.0 =0 <1.0.477)

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