CVE-2026-73314
Severity CVSS v4.0:
HIGH
Type:
Unavailable / Other
Publication date:
08/09/2026
Last modified:
09/09/2026
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.
Impact
Base Score 4.0
8.70
Severity 4.0
HIGH
Base Score 3.x
7.50
Severity 3.x
HIGH
References to Advisories, Solutions, and Tools
- https://bombobombone.github.io/posts/cve-2026-73314/
- https://github.com/BomboBombone/CVE-2026-73314
- https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook
- https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/
- https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/