Vulnerability in Xenforo
CVE-2026-73316
XenForo before 2.3.13 contains a payment replay vulnerability in the PayPal REST payment provider that allows attackers to process the same webhook payload multiple times by exploiting a missing duplicate transaction ID check. Attackers can replay a valid webhook payload to trigger duplicate payment events, resulting in repeated subscription activations and unauthorized account upgrades.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- disclosure@vulncheck.com (vendor-advisory, patch)
- disclosure@vulncheck.com (release-notes)
- disclosure@vulncheck.com (third-party-advisory)
- disclosure@vulncheck.com (technical-description)
- disclosure@vulncheck.com (exploit)
Frequently asked questions
- What is CVE-2026-73316?
- CVE-2026-73316 is a high-severity vulnerability in Xenforo, classified under Insufficient Verification of Data Authenticity. CVSS score: 7.5/10. Published 2026-09-08.
- How severe is CVE-2026-73316?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2026-73316 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.