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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是Xenforo公司的一款支持在线论坛社区讨论与内容管理的软件组件。 XenForo 2.3.13之前版本存在处理逻辑错误漏洞，该漏洞源于OAuth2令牌端点中PHP真实性评估逻辑将空字符串视为false，跳过客户端密钥验证和PKCE代码验证器验证，未经身份验证的攻击者可通过提交client_secret和code_verifier参数的空值获取有效令牌对，导致身份验证绕过。

CVSS 7.4 · High EPSS 0.69% · P52

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
Vulnerability Title
XenForo 处理逻辑错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
XenForo是Xenforo公司的一款支持在线论坛社区讨论与内容管理的软件组件。 XenForo 2.3.13之前版本存在处理逻辑错误漏洞，该漏洞源于OAuth2令牌端点中PHP真实性评估逻辑将空字符串视为false，跳过客户端密钥验证和PKCE代码验证器验证，未经身份验证的攻击者可通过提交client_secret和code_verifier参数的空值获取有效令牌对，导致身份验证绕过。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

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