CVE-2026-13447Network attack vector

Unauthenticated account access via forged Firebase JWTs

Published Sep 5, 2026 · Updated Sep 7, 2026

Authentication bypass in FluxBuilder MStore API 4.20.0 and earlier allows remote attackers to access WordPress accounts via forged JWTs. FirebasePhoneAuthHelper::verify_id_token() checks token claims but never verifies the JWT signature against Google's public key certificates. No credentials or user interaction are required; a self-signed token can impersonate any phone number to enter an existing account or create an arbitrary account.

CVSS severity9.8
Critical
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in FluxBuilder MStore API 4.20.0 and earlier allows remote attackers to access WordPress accounts via forged JWTs. FirebasePhoneAuthHelper::verify_id_token() checks token claims but never verifies the JWT signature against Google's public key certificates. No credentials or user interaction are required; a self-signed token can impersonate any phone number to enter an existing account or create an arbitrary account.

The record

CVE
CVE-2026-13447
Published
Sep 5, 2026
Updated
Sep 7, 2026
Vendor
FluxBuilder
Product
MStore API
Classifications
CWE-287, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 7, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=4.20.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

FluxBuilder · MStore APIversion=0 <=4.20.0

Published CVSS scores

9.8WordfenceCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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