CVE-2026-73311

XenForo < 2.3.13 OAuth2 Authorization Code Reuse

9.1 CriticalPublic exploit

XenForo before 2.3.13 contains an OAuth2 authorization code reuse vulnerability that allows attackers to obtain unauthorized token pairs by submitting a previously used authorization code. Attackers can exploit the failure to invalidate or mark authorization codes as consumed after initial token issuance to receive an independent token pair for the same user and scopes, bypassing the single-use guarantee of the OAuth2 authorization code flow.

Attack profile

How easy it is to exploit

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

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: None

Exploit likelihood

0.50%Up 0.1 points since Sep 9, 2026

What each source reports

CVE List Score used 9.1

XenForo < 2.3.13 OAuth2 Authorization Code Reuse

Record: CVE-2026-73311
CVSS 4.0: 9.1 CriticalCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1: 7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness: CWE-294
Updated: 2026-11-02

EUVDEUVD-2026-72782 9.1

Record: EUVD-2026-72782
CVSS 4.0: 9.1 CriticalCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-mrq5-6m75-wpj5 9.1

XenForo before 2.3.13 contains an OAuth2 authorization code reuse vulnerability that allows...

Record: GHSA-mrq5-6m75-wpj5
CVSS 4.0: 9.1 CriticalCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/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: 7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness: CWE-294
Updated: 2026-11-02

NVD 9.1

Record: CVE-2026-73311
CVSS 4.0: 9.1 CriticalCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/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: 7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness: CWE-294
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-2026-73311	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-2026-73311 is a critical vulnerability (CVSS 9.1) in Xenforo, published September 8, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 0.50%, the 42nd percentile. No source names a fixed version.