WooCommerce Subscriptions < 9.1.0 - Unauthenticated RCE via PHP Object Injection (CVE-2026-18391) | HOL Guard CVE

Critical · CVSS 9.8CVE-2026-18391

WooCommerce Subscriptions < 9.1.0 - Unauthenticated RCE via PHP Object Injection

Answer in brief

CVE-2026-18391 records a Critical severity (CVSS 9.8) vulnerability in WooCommerce Subscriptions < 9.1.0 - Unauthenticated RCE via PHP Object Injection. The current sources do not mark it as known exploited. The current feed maps Unknown/WooCommerce Subscriptions (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 12, 2026Updated Aug 26, 2026Source checked Sep 26, 2026First seen by HOL Aug 12, 2026Material review Aug 26, 2026

Upstream Advisory

Key facts

Risk: Critical · CVSS 9.8
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 9.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Unknown/WooCommerce Subscriptions (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Unknown/WooCommerce Subscriptionsgeneric	>=4.7.0 <9.1.0	9.1.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for Unknown/WooCommerce Subscriptions.
Review the reported fix. Update Unknown/WooCommerce Subscriptions to 9.1.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 12, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 26, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 12, 2026

Sources and claim methodology

Source referencewpscan.com

Upstream source description

The WooCommerce Subscriptions WordPress plugin before 9.1.0 does not validate user input before unserializing it on stores with High-Performance Order Storage enabled, leading to a PHP Object Injection issue which unauthenticated users can escalate to Remote Code Execution via a gadget chain present in the bundled dependencies.

Quoted source text, attributed separately from HOL analysis.