9.8 CVSS: Sipay OpenCart 26.8.2-26.9.0 Users Urged to Patch Signature Spoofing Vulnerability

A critical security vulnerability in the Sipay OpenCart Virtual POS Module allows attackers to forge cryptographic signatures, potentially compromising the integrity of payment transactions. The National Vulnerability Database (NVD) has assigned the flaw CVE-2026-85531 and rated it with a CVSS score of 9.8, the highest possible severity level. This issue stems from improper verification of cryptographic signatures, enabling signature spoofing through inadequate validation processes.

The risk

The core of the vulnerability lies in how the module handles cryptographic signature verification. According to the NVD record, the flaw is categorized under CWE-347, which denotes improper verification of a cryptographic signature. In secure payment systems, digital signatures ensure that transaction data has not been altered and originates from a trusted source. When this validation is improper, an attacker can craft fake signatures that the system accepts as legitimate. This allows for signature spoofing, where malicious actors can inject fraudulent data into the payment process without detection by the module’s security checks.

Who is exposed

The vulnerability affects specific versions of the Sipay OpenCart Virtual POS Module. The NVD record states that the issue impacts versions starting from 26.8.2 up to, but not including, 26.9.1. Any merchant or developer using the Sipay Electronic Money and Payment Services Inc. module within this version range is exposed to this risk. Systems running version 26.9.1 or later are not affected by this specific vulnerability, as the flaw is present only in the earlier release window.

Cost and compliance

The source material does not provide details on financial losses, regulatory fines, or specific compliance impacts resulting from this vulnerability. The NVD record focuses solely on the technical classification and affected software versions.

What should you do?

Managers should immediately audit their OpenCart installations to determine if they are running the Sipay Virtual POS Module versions 26.8.2 through 26.9.0. If the affected version is in use, prioritize updating to version 26.9.1 or later to mitigate the risk of signature spoofing.

What to do and how to stay safe: Sipay

• Inventory all OpenCart installations to identify which servers are running the Sipay Virtual POS Module.
• Check the current version number of the module against the affected range (26.8.2 to 26.9.0).
• If the module is within the affected range, schedule an immediate update to version 26.9.1 once the vendor provides the update.
• Monitor transaction logs for any anomalies that might indicate unauthorized signature manipulation while updates are pending.

Step-by-step guide: Zero-Day Vulnerabilities Meaning: How Unpatched Flaws Bypass Your Defenses

General security guidance from the Vector Tribune newsroom. It is not confirmed advice from the organisations named in this story.

Frequently asked questions

What is CVE-2026-85531?

CVE-2026-85531 is a critical vulnerability in the Sipay OpenCart Virtual POS Module that allows signature spoofing due to improper cryptographic signature verification.

Which versions of the Sipay module are affected?

The vulnerability affects the Sipay OpenCart Virtual POS Module from version 26.8.2 up to, but not including, version 26.9.1.

How severe is this vulnerability?

The National Vulnerability Database rates CVE-2026-85531 as Critical with a CVSS score of 9.8.