What is the CVSS score of CVE-2026-27591?

CVE-2026-27591 has a CVSS 3.1 base score of 9.9 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. EPSS exploitation probability: 0.1%.

Which versions of PHP are affected by CVE-2026-27591?

A critical vulnerability (CVSS 9.9) in Winter CMS poses an immediate risk to organizations using this platform, potentially allowing attackers to gain unauthorized access or execute malicious code.. A patch is available.

How to fix or mitigate CVE-2026-27591?

Within 24 hours: Identify all systems running Winter CMS and assess exposure; isolate critical instances if possible and enable enhanced monitoring. Within 7 days: Implement compensating controls (WAF rules, network segmentation, disable vulnerable features); establish incident response procedures. Within 30 days: Develop a contingency plan for migration or upgrade; monitor vendor communications for patch availability; conduct security assessment of affected systems.

PHP CVE-2026-27591

CRITICAL

Improper Access Control (CWE-284)

2026-03-11 security-advisories@github.com

GHSA-pgpf-m8m4-6cg6

PHP Laravel

9.9

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

9.9 CRITICAL

AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

Analysis Generated

Mar 12, 2026 - 22:07 vuln.today

CVE Published

Mar 11, 2026 - 22:16 nvd

CRITICAL 9.9

DescriptionGitHub Advisory

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.