---
id: CVE-2026-73314
title: >-
  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_…
summary: >-
  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_…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'
cwe:
  - CWE-754
vendor: xenforo
product: xenforo
affected:
  - xenforo < 2.3.13
patched:
  - xenforo 2.3.13
published: '2026-09-08'
updated: '2026-09-11'
sourceUpdated: '2026-09-11T20:31:16.703'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-73314'
references:
  - url: 'https://bombobombone.github.io/posts/cve-2026-73314/'
    label: disclosure@vulncheck.com
  - url: 'https://github.com/BomboBombone/CVE-2026-73314'
    label: disclosure@vulncheck.com
  - url: >-
      https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook
    label: disclosure@vulncheck.com
  - url: >-
      https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/
    label: disclosure@vulncheck.com
  - url: >-
      https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/
    label: disclosure@vulncheck.com
tags:
  - nvd
  - exploit-available
  - cve.org
epss: 0.00651
epssPercentile: 0.49034
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/BomboBombone/CVE-2026-73314'
  checkedAt: '2026-09-26T09:05:58.807Z'
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'yes'
  technicalImpact: partial
  timestamp: '2026-09-10T13:46:00.578050Z'
ingestedAt: '2026-09-08T15:33:26.984Z'
---

## Overview

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

- `xenforo < 2.3.13`

## Remediation

Upgrade past the affected range:

- `xenforo 2.3.13`