CVE-2026-73314
XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook
CVSS Score
7.5
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-754 |
| Vendor | xenforo |
| Product | xenforo |
| Published | Sep 8, 2026 |
| Last Updated | Sep 10, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None
Affected Versions
XenForo / XenForo
0 < 2.3.13
References
xenforo.com: https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/ xenforo.com: https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/ bombobombone.github.io: https://bombobombone.github.io/posts/cve-2026-73314/ github.com: https://github.com/BomboBombone/CVE-2026-73314 vulncheck.com: https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook
Credits
Marco Paciaroni (BomboBombone) VulnCheck