CVE-2026-73314

XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook

8.7 HighPublic exploit

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: High
Availability: None

Exploit likelihood

0.65%Up 0.2 points since Sep 9, 2026

What each source reports

CVE List Score used 8.7

XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook

Record: CVE-2026-73314
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness: CWE-754
Updated: 2026-11-02

EUVDEUVD-2026-72785 8.7

Record: EUVD-2026-72785
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-rqwm-9m4j-f7g3 8.7

XenForo before 2.3.13 contains a signature verification logic error in the PayPal REST webhook...

Record: GHSA-rqwm-9m4j-f7g3
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness: CWE-754
Updated: 2026-11-02

NVD 8.7

Record: CVE-2026-73314
CVSS 4.0: 8.7 HighCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness: CWE-754
Updated: 2026-11-02

Affected products

xenforo

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
Source	Link	Date
PoC in GitHub	BomboBombone/CVE-2026-73314	2026-09-08

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-73314 is a high vulnerability (CVSS 8.7) in Xenforo, published September 8, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 0.65%, the 51st percentile. No source names a fixed version.