CVE-2026-33661: Pay is an open-source payment SDK extension package for various Chinese payment services

Q: How do I fix CVE-2026-33661?

pay: upgrade to 3.7.20. Exact commands for each OS are on this page.

Q: Is CVE-2026-33661 being exploited?

CVE-2026-33661 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-33661 affect?

CVE-2026-33661 affects pay. Severity is high (CVSS 8.6). 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 re

Q: How urgent is CVE-2026-33661?

Priority 51/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 8.6REMOTEUPGRADE

CVE-2026-33661 is a high-severity flaw (CVSS 8.6) affecting pay. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 entir

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	8.6 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 56%)
CISA exploited list	No
Weakness	CWE-290
Published	2026-03-26
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: yansongda

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-26 22:16 UTCPublished CVE record published
2026-06-17 10:37 UTCUpdated Record last modified

yansongda pay UPGRADE

Affected: < 3.7.20

Fixed in: 3.7.20

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy pay || rpm -q pay || pay --version

2. UPGRADE to 3.7.20 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade pay

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pay

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-33661?

pay: upgrade to 3.7.20. Exact commands for each OS are on this page.

Is CVE-2026-33661 being exploited?

CVE-2026-33661 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-33661 affect?

CVE-2026-33661 affects pay. Severity is high (CVSS 8.6). 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 re

How urgent is CVE-2026-33661?

Priority 51/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

PHP vulnerabilities

References

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