CVE-2020-23533Public exploitNetwork attack vector

Payment forgery via null MAC key

Published Apr 6, 2021 · Updated Aug 4, 2024

Improper verification in UnionPay PHP SDK up to 1.2.0 allows remote attackers to obtain free purchases via forged payment notifications. The validate() routine lets a supplied signMethod select MAC verification and accepts a null secureKey when configuration omits it, so attackers can compute a valid MAC and impersonate the cashier server. Exploitation requires a merchant server using the affected SDK and exposed notification URL; the demonstrated consequence is fraudulent transactions and integrity loss.

CVSS severity7.5
High
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper verification in UnionPay PHP SDK up to 1.2.0 allows remote attackers to obtain free purchases via forged payment notifications. The validate() routine lets a supplied signMethod select MAC verification and accepts a null secureKey when configuration omits it, so attackers can compute a valid MAC and impersonate the cashier server. Exploitation requires a merchant server using the affected SDK and exposed notification URL; the demonstrated consequence is fraudulent transactions and integrity loss.

The record

CVE
CVE-2020-23533
Published
Apr 6, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-347
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
5.0NVDAV:N/AC:L/Au:N/C:N/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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