Vulnerability in Yansongda Pay
CVE-2026-33661
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.007 (50.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 50th percentile — 50.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.007 · change: +0.002
Affected products
- Yansongda Pay — versions < 3.7.20
Weakness classification (CWE)
References
- github.com/yansongda/pay/security/advisories/GHSA-q938-ghwv-8gvc (Exploit, Vendor Advisory)
- github.com/yansongda/pay/commit/26987ebf789f1e7f0a85febb640986ab4289fd7f (Patch)
- github.com/yansongda/pay/releases/tag/v3.7.20 (Release Notes)
Frequently asked questions
- What is CVE-2026-33661?
- CVE-2026-33661 is a high-severity vulnerability in Yansongda Pay, classified under Authentication Bypass by Spoofing. CVSS score: 8.6/10. Published 2026-03-26.
- How severe is CVE-2026-33661?
- High severity. CVSS v3 base score is 8.6 out of 10.