[CRITICAL] CVE-2026-78003 — CVSS 9.8 (August 22, 2026)

A CRITICAL-severity vulnerability identified as CVE-2026-78003 has been published on August 22, 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-2026-78003
Severity: CRITICAL
CVSS Score: 9.8
Published: August 22, 2026
Weakness (CWE): CWE-918

Technical Description

The Mailgun for WordPress plugin for WordPress is vulnerable to Server-Side Request Forgery (SSRF) via path traversal in versions up to and including 2.2.0. This is due to insufficient input validation in the add_list() function, which accepts user-controlled array keys from $_POST['addresses'], passes them through sanitize_text_field(). This makes it possible for unauthenticated attackers to make authenticated POST requests to any Mailgun API endpoint using the WordPress site's API key, including creating inbound email-forwarding routes that can intercept password reset emails, leading to administrator account takeover.

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

• Reference 1
• Reference 2
• Reference 3
• Reference 4
• Reference 5

Related Security Advisories

• [HIGH] CVE-2026-18353 — CVSS 8.8 (July 30, 2026) — HIGH / CVSS 8.8
• [HIGH] CVE-2026-2053 — CVSS 8.3 (June 26, 2026) — HIGH / CVSS 8.3
• [CRITICAL] CVE-2024-13784 — CVSS 9.8 (August 16, 2026) — CRITICAL / CVSS 9.8