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CVE-2026-73309— XenForo < 2.3.13 Authentication Bypass via OAuth2 Token Endpoint

Quick assessment

Affected
XenForo XenForo
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

XenForo 在 2.3.13 之前版本中存在一个身份验证绕过漏洞，位于 OAuth2 令牌端点。该漏洞允许未经身份验证的攻击者通过为 和 参数提交空值，从而获取有效的令牌对。攻击者可利用 PHP 的“真值”评估逻辑——该逻辑将空字符串视为 ，从而跳过客户端密钥验证和 PKCE 码验证器验证——在没有证明客户端身份或不持有 PKCE 承诺的情况下，使用有效的授权码换取令牌对。

CVSS 7.4 · High

Possible ATT&CK Techniques 1 AI

T1083 · File and Directory Discovery

Affected Version Matrix 1

VendorProduct Version RangeStatus
XenForo XenForo < 2.3.13 affected
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I. Basic Information for CVE-2026-73309

Vulnerability Information
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Vulnerability Title
XenForo < 2.3.13 Authentication Bypass via OAuth2 Token Endpoint
Source: CVE Program / CVE List V5
Vulnerability Description
XenForo before 2.3.13 contains an authentication bypass vulnerability in the OAuth2 token endpoint that allows unauthenticated attackers to obtain valid token pairs by submitting empty values for client_secret and code_verifier parameters. Attackers can exploit PHP truthy evaluation logic, which treats empty strings as false and skips client secret validation and PKCE code verifier validation, to exchange a valid authorization code for a token pair without proving client identity or holding the PKCE commitment.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
不充分的比较
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
XenForo XenForo 0 ~ 2.3.13 -

II. Public POCs for CVE-2026-73309

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III. Intelligence Information for CVE-2026-73309

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Vendor Advisories for CVE-2026-73309 (1)

Exploits & Public PoCs for CVE-2026-73309 (1)

Security Blog Posts for CVE-2026-73309 (1)

Same Patch Batch · XenForo · 2026-09-08 · 14 CVEs total

CVE-2026-73315 8.6 HIGH XenForo < 2.3.13 SSRF via PayPal REST Webhook Handler
CVE-2026-73314 7.5 HIGH XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook
CVE-2026-73316 7.5 HIGH XenForo < 2.3.13 Payment Replay via PayPal REST Payment Provider
CVE-2026-73311 7.4 HIGH XenForo < 2.3.13 OAuth2 Authorization Code Reuse
CVE-2026-73312 7.4 HIGH XenForo < 2.3.13 Refresh Token Replay via Expired Access Token
CVE-2026-74239 7.2 HIGH XenForo < 2.3.13 Path Traversal via Style Archive Importer on Windows
CVE-2026-73313 6.8 MEDIUM XenForo < 2.3.13 MFA Bypass via Passkey TFA Provider
CVE-2026-73321 6.5 MEDIUM XenForo < 2.3.13 Uncontrolled Recursion DoS via BBCode Parser
CVE-2026-73320 6.1 MEDIUM XenForo < 2.3.13 Unauthenticated Information Disclosure via Unfurl Endpoint
CVE-2026-73319 6.1 MEDIUM XenForo < 2.3.13 XSS via Dynamic Redirect Handler
CVE-2026-73310 5.9 MEDIUM XenForo < 2.3.13 OAuth2 Authorization Code Token Theft via redirect_uri Bypass
CVE-2026-73318 3.8 LOW XenForo < 2.3.13 Missing Authorization via force-agreement Controller
CVE-2026-73317 2.7 LOW XenForo < 2.3.13 Missing Authorization via ACP Cache-Rebuild Dispatcher

IV. Related Vulnerabilities

Same product: XenForo
Same vendor: XenForo
Same weakness: CWE-697

V. Comments for CVE-2026-73309

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