---
title: "CVE-2026-27591: Winter vulnerable to privilege escalation by authenticated backend users"
url: https://erroneo.us/security/cve/CVE-2026-27591/
description: "CVE-2026-27591 (winter/wn-backend-module (Composer (PHP))): Winter is a free, open-source content management system (CMS) based on the Laravel PHP…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-03-11
date_modified: 2026-03-12
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-27591"
kev: false
cvss: 10
epss: 0.0086
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-27591: Winter vulnerable to privilege escalation by authenticated backend users

**Signal:** Critical, preconditions apply. Severe if exploited, but exploitation needs conditions that may not apply to you. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.9% , percentile 58: FIRST’s model estimates a 0.9% chance of exploitation activity in the next 30 days, higher than 58% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes winter/wn-backend-module (Composer (PHP)) >= 1.2.0, < 1.2.12, fixed in 1.2.12 ; winter/wn-backend-module (Composer (PHP)) >= 1.1.0, < 1.1.12, fixed in 1.1.12 ; winter/wn-backend-module (Composer (PHP)) < 1.0.477, fixed in 1.0.477 . Check your lockfile, including transitive dependencies.

## What it is

Winter is a free, open-source content management system (CMS) based on the Laravel PHP framework. Prior to 1.0.477, 1.1.12, and 1.2.12, 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. This vulnerability is fixed in 1.0.477, 1.1.12, and 1.2.12.

## Affected packages

- Composer (PHP) `winter/wn-backend-module` >= 1.2.0, < 1.2.12 → fixed: 1.2.12
- Composer (PHP) `winter/wn-backend-module` >= 1.1.0, < 1.1.12 → fixed: 1.1.12
- Composer (PHP) `winter/wn-backend-module` < 1.0.477 → fixed: 1.0.477

## Affected products (CVE record)

- wintercms winter: >= 1.2.0, < 1.2.12, >= 1.1.0, < 1.1.12, < 1.0.477

## Severity

- GitHub_M CVSS 3.1: 10 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.9 `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.86% probability of exploitation activity in the next 30 days; percentile 58.

## Sources

- [GitHub Advisory GHSA-pgpf-m8m4-6cg6](https://github.com/advisories/GHSA-pgpf-m8m4-6cg6)
- [CVE.org record CVE-2026-27591](https://www.cve.org/CVERecord?id=CVE-2026-27591)
- [NVD entry CVE-2026-27591](https://nvd.nist.gov/vuln/detail/CVE-2026-27591)
- [github.com](https://github.com/wintercms/winter/security/advisories/GHSA-pgpf-m8m4-6cg6)
- [wintercms.com](https://wintercms.com/releases/v1.0.477)
- [wintercms.com](https://wintercms.com/releases/v1.1.12)
- [wintercms.com](https://wintercms.com/releases/v1.2.12)

---
Source page: https://erroneo.us/security/cve/CVE-2026-27591/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt