Vulnerability Description
Pay is an open-source payment SDK extension package for various Chinese payment services. Prior to version 3.7.20, the `verify_wechat_sign()` function in `src/Functions.php` unconditionally skips all signature verification when the PSR-7 request reports `localhost` as the host. An attacker can exploit this by sending a crafted HTTP request to the WeChat Pay callback endpoint with a `Host: localhost` header, bypassing the RSA signature check entirely. This allows forging fake WeChat Pay payment success notifications, potentially causing applications to mark orders as paid without actual payment. Version 3.7.20 fixes the issue.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Yansongda | Pay | < 3.7.20 |
Related Weaknesses (CWE)
References
- https://github.com/yansongda/pay/commit/26987ebf789f1e7f0a85febb640986ab4289fd7fPatch
- https://github.com/yansongda/pay/releases/tag/v3.7.20Release Notes
- https://github.com/yansongda/pay/security/advisories/GHSA-q938-ghwv-8gvcExploitVendor Advisory
- https://github.com/yansongda/pay/security/advisories/GHSA-q938-ghwv-8gvcExploitVendor Advisory
FAQ
What is CVE-2026-33661?
CVE-2026-33661 is a vulnerability with a CVSS score of 8.6 (HIGH). Pay is an open-source payment SDK extension package for various Chinese payment services. Prior to version 3.7.20, the `verify_wechat_sign()` function in `src/Functions.php` unconditionally skips all ...
How severe is CVE-2026-33661?
CVE-2026-33661 has been rated HIGH with a CVSS base score of 8.6/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-33661?
Check the references section above for vendor advisories and patch information. Affected products include: Yansongda Pay.