CVE-2026-31889 is an authentication bypass vulnerability classified under CWE-290, affecting the Shopware open commerce platform core. The flaw exists in the legacy app registration flow prior to versions 6.6.10.15 and 6.7.8.1. Shopware uses HMAC-based authentication to secure communication between shops and their apps. However, this mechanism does not adequately bind a shop installation to its original domain, allowing the shop URL to be updated during re-registration without verifying control over the previously registered domain. An attacker who has access to the relevant app-side secret can exploit this weakness by re-registering the app with a malicious domain under their control. This enables the attacker to hijack the communication channel between the shop and the app, redirecting API traffic and potentially capturing sensitive API credentials meant for the legitimate shop. The vulnerability affects confidentiality and integrity severely, as attackers can impersonate legitimate app communications and gain unauthorized access to API credentials. The attack requires possession of the app secret but does not require user interaction or authentication on the shop side. The vulnerability has a CVSS v3.1 score of 8.9, indicating high severity. No public exploits or active exploitation have been reported yet. The issue is resolved in Shopware versions 6.6.10.15 and 6.7.8.1 by strengthening the binding between shop installations and their domains during app registration.

This vulnerability can have significant impacts on organizations using affected versions of Shopware. Successful exploitation allows attackers to hijack app communication channels, redirect API traffic, and obtain API credentials intended for legitimate shops. This compromises the confidentiality and integrity of sensitive data exchanged between shops and their apps, potentially leading to unauthorized transactions, data leakage, or further compromise of connected systems. The availability impact is limited but could occur if attackers disrupt app communication. Organizations relying on Shopware for e-commerce operations may face financial losses, reputational damage, and regulatory consequences if customer data or transaction integrity is compromised. The attack does not require user interaction or authentication, increasing the risk of automated or targeted attacks once the app secret is obtained. Although no known exploits are reported in the wild, the high CVSS score and the nature of the vulnerability make it a critical risk to address promptly.

1. Upgrade affected Shopware installations to versions 6.6.10.15 or 6.7.8.1 or later, where the vulnerability is patched. 2. Review and rotate app-side secrets to invalidate any potentially compromised credentials. 3. Implement strict monitoring and alerting on app registration and re-registration activities to detect suspicious changes in shop URLs or app configurations. 4. Enforce domain ownership verification mechanisms during app registration and re-registration processes to ensure that only authorized parties can update shop URLs. 5. Limit exposure of app-side secrets by applying the principle of least privilege and secure storage practices. 6. Conduct regular security audits of app integrations and communication channels to identify anomalies. 7. Educate development and operations teams about secure app registration flows and the risks of insufficient domain binding. 8. Consider additional network-level protections such as DNS filtering or web application firewalls to detect and block traffic to unauthorized domains.