# CVE-2026-73314

## Summary

- **CVE ID:** CVE-2026-73314
- **Severity:** HIGH
- **CVSS Score:** 8.7 (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)
- **CWE:** CWE-754
- **Published:** Sep 8, 2026
- **Last Modified:** Sep 9, 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.

## Affected Products

- XenForo — XenForo (0)

## References

- [CNA](https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/)
- [CNA](https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/)
- [CNA](https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook)
- [CNA](https://bombobombone.github.io/posts/cve-2026-73314/)
- [CNA](https://github.com/BomboBombone/CVE-2026-73314)

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-09._