CVE-2026-73314CWE-754

CVE-2026-73314

High · published September 8, 2026

CVSS v3.1
7.5
EPSS
1%
Percentile
50.6
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v4.0
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
EPSS
0.00651 · 50.6th percentile
Weakness
CWE-754 · Improper Check for Unusual or Exceptional Conditions
Published
2026-09-08T18:17Z
Affected products (1)
ProductVersionsFixed in
xenforo/xenforo< 2.3.132.3.13
References (5)
https://bombobombone.github.io/posts/cve-2026-73314/ · [email protected]https://github.com/BomboBombone/CVE-2026-73314 · [email protected]https://www.vulncheck.com/advisories/xenforo-signature-verification-bypass-via-paypal-rest-webhook · [email protected]https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/ · [email protected]https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/ · [email protected]
EPSS history
Timeline
  • 10 SEP 03:18Z
    EPSS moved — → 0%
    epss
  • 08 SEP 13:17Z
    XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook
    cvelistv5