[CRITICAL] CVE-2026-5229 — CVSS 9.8 (May 15, 2026)

A CRITICAL-severity vulnerability identified as CVE-2026-5229 has been published on May 15, 2026 with a CVSS base score of 9.8. This security advisory provides a detailed breakdown of the vulnerability, its potential impact, weakness classification, and actionable steps to protect your systems.

Vulnerability Details

CVE ID: CVE-2026-5229
Severity: CRITICAL
CVSS Score: 9.8
Published: May 15, 2026
Weakness (CWE): CWE-287

Technical Description

The Form Notify plugin for WordPress is vulnerable to Authentication Bypass in versions up to and including 1.1.10. This is due to the plugin trusting user-controlled cookie data to determine which WordPress account to authenticate after a LINE OAuth login. When LINE doesn't provide an email address (which is common), the plugin falls back to reading the 'form_notify_line_email' cookie value without verifying that the LINE account is associated with that email address. This makes it possible for unauthenticated attackers to gain access to any user account on the site, including administrator accounts, by completing a LINE OAuth flow with their own LINE account while injecting a malicious cookie containing the target victim's email address.

Potential Impact

If exploited, this critical-severity vulnerability could allow an attacker to compromise sensitive data confidentiality, tamper with system integrity, cause a denial of service. Organizations running affected software should treat this as a priority remediation item.

Recommended Action

No official patch is available yet. Until one is released:

1. Monitor the official NVD page and vendor channels for patch announcements.
2. Restrict access to the affected system or service where possible.
3. Apply network-level mitigations such as firewall rules or WAF policies.
4. Enable logging and alerting for anomalous activity related to this vulnerability.
5. Review your incident response plan in case of active exploitation.

View full details on NVD →

References

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Related Security Advisories

• [CRITICAL] CVE-2013-10075 — CVSS 9.1 (May 8, 2026) — CRITICAL / CVSS 9.1
• [CRITICAL] CVE-2026-35547 — CVSS 9.1 (April 30, 2026) — CRITICAL / CVSS 9.1
• [CRITICAL] CVE-2026-3325 — CVSS 10.0 (April 29, 2026) — CRITICAL / CVSS 10.0