How severe is CVE-2026-66398?

CVE-2026-66398 has a CVSS 4.0 base score of 9.4, rated critical severity.

Is CVE-2026-66398 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-66398?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-66398 published?

CVE-2026-66398 was published on 2026-07-27 and last updated on 2026-07-28.

CVE-2026-66398

CVE-2026-66398 is a critical-severity vulnerability with a CVSS 4.0 base score of 9.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-494.

Key facts

Severity: Critical (CVSS 4.0 base score 9.4)
EPSS exploit prediction: 0% (16th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-494
Published: 2026-07-27
Last modified: 2026-07-28

Description

phpMyFAQ before v4.1.6 contains a remote code execution vulnerability in the configuration API that allows authenticated administrators with CONFIGURATION_EDIT and ATTACHMENT_ADD privileges to write arbitrary PHP files by manipulating the upgrade.lastDownloadedPackage setting. Attackers can upload a malicious ZIP file as an attachment, point the updater configuration to its stored path, and extract it into the application root to achieve code execution as the web server user.

Frequently asked questions

What is CVE-2026-66398?: phpMyFAQ before v4.1.6 contains a remote code execution vulnerability in the configuration API that allows authenticated administrators with CONFIGURATION_EDIT and ATTACHMENT_ADD privileges to write arbitrary PHP files by manipulating the upgrade.lastDownloadedPackage setting. Attackers can upload a malicious ZIP file as an attachment, point the updater configuration to its stored path, and extract it into the application root to achieve code execution as the web server user.
How severe is CVE-2026-66398?: CVE-2026-66398 has a CVSS 4.0 base score of 9.4, rated critical severity.
Is CVE-2026-66398 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (16th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-66398?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-66398 published?: CVE-2026-66398 was published on 2026-07-27 and last updated on 2026-07-28.

References

Other CWE-494 vulnerabilities

CVE-2020-1595 — Critical (CVSS 9.9): <p>A remote code execution vulnerability exists in Microsoft SharePoint where APIs aren't properly protected from…
CVE-2020-1210 — Critical (CVSS 9.9): <p>A remote code execution vulnerability exists in Microsoft SharePoint when the software fails to check the source…
CVE-2026-42248 — Critical (CVSS 9.8): Ollama for Windows does not perform integrity or authenticity verification of downloaded update executables. Unlike…
CVE-2026-34841 — Critical (CVSS 9.8): Bruno is an open source IDE for exploring and testing APIs. Prior to 3.2.1, Bruno was affected by a supply chain attack…
CVE-2026-3000 — Critical (CVSS 9.8): IDExpert Windows Logon Agent developed by Changing has a Remote Code Execution vulnerability, allowing unauthenticated…
CVE-2026-2999 — Critical (CVSS 9.8): IDExpert Windows Logon Agent developed by Changing has a Remote Code Execution vulnerability, allowing unauthenticated…

Browse all CWE-494 vulnerabilities →