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Noroxi
NVD / CVE Program· CNA WPScan

CVE-2026-16038: MStore API < 4.21.0 - Unauthenticated Payment Bypass via Multiple Payment Gateways

Noroxi assessment

Priority: Monitor (action score 36/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.41% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Unknown MStore API 4.21.0.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Unknown MStore API 4.21.0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

CriticalCVSS 9.1 · v3.1—No exploit Fix available
Published
Aug 7, 2026
Updated
Aug 26, 2026
EPSS
0.4% · 36th percentile

Report tools

JSON

Action score

36

Monitor

Low priority for now.

CVSS
36 / 40 · 9.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
proof of concept
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

Is MStore API – Create Native Android & iOS Apps On The Cloud on your site?

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When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (WPScan). Independent of NVD's CPE analysis and usually ahead of it.

  • Unknown MStore API

    • before 4.21.0affected · semver

Same product

unknown: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-16030MStore API < 4.21.0 - Unauthenticated Account Takeover via Firebase Phone Authentication
    32Monitor
  • CVE-2026-16041MStore API < 4.21.0 - Unauthenticated Product Review Creation
    30Monitor
  • CVE-2026-18234MStore API < 4.21.1 - Subscriber+ Arbitrary Order Payment Bypass via Wallet
    26Monitor

Published before and after this one in the same product

  • Later →CVE-2026-16039Aug 7, 2026 · MStore API < 4.21.0 - Subscriber+ Order and Customer PII Disclosure via IDOR
    26Monitor
  • Later →CVE-2026-18233Aug 29, 2026 · MStore API < 4.21.1 - Subscriber+ Arbitrary Order Completion
    26Monitor
  • Later →CVE-2026-97219Oct 2, 2026 · MStore API 4.21.1 - 4.22.0 - Subscriber+ Payment Bypass via 'status' Parameter
    17Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Unknown MStore API4.21.0Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-160410 days apartMStore API < 4.21.0 - Unauthenticated Product Review Creation
    30Monitor
  • CVE-2026-1823322 days apartMStore API < 4.21.1 - Subscriber+ Arbitrary Order Completion
    26Monitor
  • CVE-2026-1823422 days apartMStore API < 4.21.1 - Subscriber+ Arbitrary Order Payment Bypass via Wallet
    26Monitor
  • CVE-2026-9721956 days apartMStore API 4.21.1 - 4.22.0 - Subscriber+ Payment Bypass via 'status' Parameter
    17Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
None

Weakness class (CWE)

CWE-862 · Missing Authorization

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records