TI-2026-21979 Aliases CVE-2026-27591 GHSA-pgpf-m8m4-6cg6

Winter: Privilege escalation by authenticated backend users

MEDIUM 44CWE-284Published 2026-03-11 · Updated 2026-03-12

Key facts

Attack vector: Network
Privileges required: Low
User interaction: None
Attack complexity: Low
Impact type: Security bypass, Tampering
Confidentiality · integrity · availability: High · High · High
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-284 and CWE-915.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00777 56th percentileScored 2026-11-07

Fix Fixed winter (wintercms): 1.2.12, 1.1.12, 1.0.477winter/wn-backend-module (Packagist): 1.2.12, 1.1.12, 1.0.477

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
wintercms	winter	1.2.0 to before 1.2.12; 1.1.0 to before 1.1.12; before 1.0.477	1.2.12, 1.1.12, 1.0.477	Patch available	CNA
—	winter/wn-backend-module (Packagist)	1.2.0 to before 1.2.12	1.2.12	Patch available	GHSA-pgpf-m8m4-6cg6
—	winter/wn-backend-module (Packagist)	1.1.0 to before 1.1.12	1.1.12	Patch available	GHSA-pgpf-m8m4-6cg6
—	winter/wn-backend-module (Packagist)	before 1.0.477	1.0.477	Patch available	GHSA-pgpf-m8m4-6cg6

winter Vendorwintercms Affected 1.2.0 to before 1.2.12; 1.1.0 to before 1.1.12; before 1.0.477 Fixed in 1.2.12, 1.1.12, 1.0.477 Patch available CNA
winter/wn-backend-module (Packagist) Vendor— Affected 1.2.0 to before 1.2.12 Fixed in 1.2.12 Patch available GHSA-pgpf-m8m4-6cg6
winter/wn-backend-module (Packagist) Vendor— Affected 1.1.0 to before 1.1.12 Fixed in 1.1.12 Patch available GHSA-pgpf-m8m4-6cg6
winter/wn-backend-module (Packagist) Vendor— Affected before 1.0.477 Fixed in 1.0.477 Patch available GHSA-pgpf-m8m4-6cg6

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:wintercms:winter::::::::	before 1.0.477; 1.1.0 to before 1.1.12; 1.2.0 to before 1.2.12	Vulnerable	wintercms

cpe:2.3:a:wintercms:winter:*:*:*:*:*:*:*:* Versions before 1.0.477; 1.1.0 to before 1.1.12; 1.2.0 to before 1.2.12 Vulnerable ·wintercms

Remediation

Fix · CNA winter (wintercms) Fixed in 1.2.12, 1.1.12, 1.0.477
Fix · GHSA-pgpf-m8m4-6cg6 winter/wn-backend-module (Packagist) Fixed in 1.2.12 Advisory →
Fix · GHSA-pgpf-m8m4-6cg6 winter/wn-backend-module (Packagist) Fixed in 1.1.12 Advisory →
Fix · GHSA-pgpf-m8m4-6cg6 winter/wn-backend-module (Packagist) Fixed in 1.0.477 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-27591
2026-10-03 Alias added: GHSA-pgpf-m8m4-6cg6

References

Patch 1

https://github.com/wintercms/winter/security/advisories/GHSA-pgpf-m8m4-6cg6

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-27591

Other 4

TI-2024-19497 Server-side Template Injection (SSTI) vulnerability in Winter CMS v.1.2.3 allows a remote… CVSS 3.1HIGH 7.2
TI-2023-28528 Winter CMS Local File Inclusion through Server Side Template Injection CVSS 3.1MEDIUM 5.4
TI-2022-18732 Winter vulnerable to Prototype Pollution in Snowboard framework CVSS 3.1CRITICAL 9.8
TI-2024-36264 Winter CMS Modules allows a sandbox bypass in Twig templates leading to data modification and deletion CVSS 3.1HIGH 8.5
TI-2023-18899 Winter CMS vulnerable to stored XSS through privileged upload of SVG file CVSS 3.1MEDIUM 4.8
TI-2023-28527 Winter CMS Stored XSS through Backend ColorPicker FormWidget CVSS 3.1MEDIUM 5.4

See all 8 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences