CVE-2026-27591: Winter/wn backend module Winter Vulnerable To Privilege Escalation Vulnerability
CRITICALCVE-2026-27591 is a CRITICAL (CVSS 9.9) winter vulnerable to privilege escalation vulnerability (CWE-284: Improper Access Control) affecting Winter/wn backend module libraries in the Packagist ecosystem. The issue involves winter vulnerable to privilege escalation by authenticated backend users. Remediation is available by upgrading affected packages to version 1.2.12, 1.1.12, 1.0.477.
CVE-2026-27591 at a Glance
Security Impact
CVSS: 9.9
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H).
How to Fix CVE-2026-27591
To remediate this vulnerability, upgrade all affected Winter/wn backend module dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade winter/wn-backend-module to 1.2.12Upgrade winter/wn-backend-module to 1.1.12Upgrade winter/wn-backend-module to 1.0.477Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for winter/wn-backend-moduleHow to Check if You Are Affected
To determine whether your application is affected by CVE-2026-27591, inspect your project dependencies for Winter/wn backend module:
inspect dependencies for winter/wn-backend-moduleAnalyze the terminal output to locate any version of Winter/wn backend module in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.2.12), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-284: Improper Access Control, where the product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. In Winter/wn backend module, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-27591 Affected Winter/wn backend module Versions
3 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
winter/wn-backend-module
|
Packagist |
≥ 1.2.0
< 1.2.12
|
1.2.12
|
|
winter/wn-backend-module
|
Packagist |
≥ 1.1.0
< 1.1.12
|
1.1.12
|
|
winter/wn-backend-module
|
Packagist |
< 1.0.477
|
1.0.477
|
References
Frequently Asked Questions
What is CVE-2026-27591?
Which Winter/wn backend module versions are affected?
What version fixes CVE-2026-27591?
Is winter/wn-backend-module affected?
What is the CVSS score of CVE-2026-27591?
What CWE is associated with CVE-2026-27591?
How can I check Packagist dependencies for CVE-2026-27591?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-pgpf-m8m4-6cg6",
"modified" : "2026-03-12T14:07:39Z",
"published" : "2026-03-12T14:07:39Z",
"aliases" : [ "CVE-2026-27591" ],
"summary" : "Winter vulnerable to privilege escalation by authenticated backend users",
"details" : "## Impact\nAffected 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.\n\nTo actively exploit this security issue, an attacker would need access to the Backend with a user account with any level of access.\n\nThe 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).\n\n## Patches\nMultiple fixes and defence in depth has been applied to prevent current and future privilege escalation attacks at the lowest level possible.\n\nThis 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.\n\n## Workarounds\nIf you cannot upgrade, you may apply the changes from the releases to your Winter CMS installation manually to resolve this issue.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Packagist",
"name" : "winter/wn-backend-module"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.2.0"
}, {
"fixed" : "1.2.12"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Packagist",
"name" : "winter/wn-backend-module"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "1.1.0"
}, {
"fixed" : "1.1.12"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Packagist",
"name" : "winter/wn-backend-module"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "1.0.477"
} ]
} ]
} ],
"references" : [ {
"type" : "WEB",
"url" : "https://github.com/wintercms/winter/security/advisories/GHSA-pgpf-m8m4-6cg6"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-27591"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/wintercms/winter"
}, {
"type" : "WEB",
"url" : "https://wintercms.com/releases/v1.0.477"
}, {
"type" : "WEB",
"url" : "https://wintercms.com/releases/v1.1.12"
}, {
"type" : "WEB",
"url" : "https://wintercms.com/releases/v1.2.12"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-284", "CWE-639", "CWE-915" ],
"severity" : "CRITICAL",
"github_reviewed" : true,
"github_reviewed_at" : "2026-03-12T14:07:39Z",
"nvd_published_at" : "2026-03-11T22:16:32Z"
}
}