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.
Advisories

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Fixes

Solution

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Workaround

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History

Fri, 11 Sep 2026 23:45:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:xenforo:xenforo:*:*:*:*:*:*:*:*

Thu, 10 Sep 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 09 Sep 2026 01:15:00 +0000


Tue, 08 Sep 2026 15:30:00 +0000

Type Values Removed Values Added
First Time appeared Xenforo
Xenforo xenforo
Vendors & Products Xenforo
Xenforo xenforo

Tue, 08 Sep 2026 13:30:00 +0000

Type Values Removed Values Added
Description 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.
Title XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook
Weaknesses CWE-754
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}

cvssV4_0

{'score': 8.7, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-10-01T15:20:34.739Z

Reserved: 2026-08-11T19:56:20.007Z

Link: CVE-2026-73314

cve-icon Vulnrichment

Updated: 2026-09-10T13:46:12.695Z

cve-icon NVD

Status : Analyzed

Published: 2026-09-08T14:17:25.640

Modified: 2026-09-11T20:31:16.703

Link: CVE-2026-73314

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-08T15:15:17Z

Weaknesses