CVE-2026-73314

XenForo before 2.3.13 contains a signature verification logic error in the PayPal REST webhook handler that allows unauthenticated attackers to bypass payment signature validation by submitting a webhook request with an unsupported auth_algo header value. When the algorithm cannot be mapped to a supported hash function, the verification function incorrectly returns true instead of failing, causing the caller to treat the fabricated request as verified and process the payment event without a valid PayPal signature.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://bombobombone.github.io/posts/cve-2026-73314/	Exploit Third Party Advisory
https://github.com/BomboBombone/CVE-2026-73314	Exploit Third Party Advisory
https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook	Third Party Advisory
https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/	Release Notes
https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/	Release Notes

Configurations

Configuration 1 (hide)

cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-09-08 14:17

Updated : 2026-09-11 20:31

NVD link : CVE-2026-73314

Mitre link : CVE-2026-73314

CVE.ORG link : CVE-2026-73314

JSON object : View

Products Affected

xenforo

xenforo

CWE

CWE-754

Improper Check for Unusual or Exceptional Conditions

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