CVE-2026-73314Public exploitNetwork attack vector

Forged payment events via unsupported signature algorithm

Published Sep 8, 2026 · Updated Sep 10, 2026

Signature verification bypass in XenForo before 2.3.13 allows remote attackers to inject fabricated PayPal REST payment events. The PayPal REST webhook verification routine returns true when an untrusted auth_algo header does not map to a supported hash function. A reachable PayPal REST callback is sufficient; no XenForo account, user interaction, or valid PayPal signature is required, and impact is limited to unauthorized payment-event processing.

CVSS severity8.7
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Signature verification bypass in XenForo before 2.3.13 allows remote attackers to inject fabricated PayPal REST payment events. The PayPal REST webhook verification routine returns true when an untrusted auth_algo header does not map to a supported hash function. A reachable PayPal REST callback is sufficient; no XenForo account, user interaction, or valid PayPal signature is required, and impact is limited to unauthorized payment-event processing.

The record

CVE
CVE-2026-73314
Published
Sep 8, 2026
Updated
Sep 10, 2026
Vendor
XenForo Ltd.
Product
XenForo
Classifications
CWE-754, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <2.3.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

XenForo Ltd. · XenForoversion=0 <2.3.13

Published CVSS scores

8.7VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
7.5VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
T1190Exploit Public-Facing Application

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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