CVE-2026-9027: Signature Bypass (CVSS 5.3)

Description

The CorvusPay WooCommerce Payment Gateway plugin for WordPress is vulnerable to Payment Bypass via Improper Verification of Cryptographic Signature in all versions up to, and including, 2.7.4. The `corvuspay_success_handler` function registers the REST endpoint `POST /wp-json/corvuspay/success/` with `'permission_callback' => '__return_true'`, and while it calls `$this->client->validate->signature()` and stores the boolean result in `$res`, the result is never evaluated in a conditional — it is only written to the debug log — causing execution to unconditionally reach `$order->payment_complete()` regardless of whether the cryptographic signature is valid. This makes it possible for unauthenticated attackers to mark any pending WooCommerce order as fully paid by sending a POST request to the success endpoint containing an arbitrary or forged signature value, allowing them to obtain goods or services without payment. Because WooCommerce order IDs are sequential integers, target orders are trivially enumerable via the `order_number` POST parameter, requiring no prior knowledge of the victim order.

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CVSS v3.1 Score

5.3

MEDIUM

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

EPSS — Exploit Prediction

0.0022

Probability of exploitation

0.13%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-347 CWE-347

References

Other References

Frequently Asked Questions

What is CVE-2026-9027? +

The CorvusPay WooCommerce Payment Gateway plugin for WordPress is vulnerable to Payment Bypass via Improper Verification of Cryptographic Signature in all versions up to, and including, 2.7.4. The `corvuspay_success_handler` function registers the REST endpoint `POST /wp-json/corvuspay/success/` with `'permission_callback' => '__return_true'`, and while it calls `$this->client->validate->signature()` and stores the boolean result in `$res`, the result is never evaluated in a conditional — it is only written to the debug log — causing execution to unconditionally reach `$order->payment_complete()` regardless of whether the cryptographic signature is valid. This makes it possible for unauthenticated attackers to mark any pending WooCommerce order as fully paid by sending a POST request to the success endpoint containing an arbitrary or forged signature value, allowing them to obtain goods or services without payment. Because WooCommerce order IDs are sequential integers, target orders are trivially enumerable via the `order_number` POST parameter, requiring no prior knowledge of the victim order. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2026-9027? +

CVE-2026-9027 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0022, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-9027? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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