Auth bypass in Mstore API

CVE-2026-16038

The MStore API WordPress plugin before 4.21.0 does not verify the payment with the payment gateway before marking an order as paid on several of its payment-completion endpoints, allowing an unauthenticated attacker to mark an arbitrary order fully paid without paying and obtain goods or services for free.

Vulnerability class: Broken Access Control

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.004 (36.1th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 36.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-16038: held from 0.004 to 0.004.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

  • Mstore API — versions 0

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-16038?
CVE-2026-16038 is a critical-severity vulnerability in Mstore API, classified under Missing Authorization. CVSS score: 9.1/10. Published 2026-08-07.
How severe is CVE-2026-16038?
Critical severity. CVSS v3 base score is 9.1 out of 10.