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CVE-2026-73314— XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook

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 2.3.13 之前的版本存在一个 PayPal REST webhook 处理器中的签名验证逻辑错误，允许未经身份验证的攻击者通过提交带有不受支持的 auth_algo 头值的 webhook 请求，从而绕过支付签名验证。当该算法无法映射到受支持的哈希函数时，验证函数错误地返回 true（而不是失败），导致调用方将伪造的请求视为已验证，并在没有有效 PayPal 签名的情况下处理支付事件。

CVSS 7.5 · High

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle

Affected Version Matrix 1

VendorProduct Version RangeStatus
XenForo XenForo < 2.3.13 affected
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I. Basic Information for CVE-2026-73314

Vulnerability Information
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Vulnerability Title
XenForo < 2.3.13 Signature Verification Bypass via PayPal REST Webhook
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对因果或异常条件的不恰当检查
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-2026-73314

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-73314

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Vendor Advisories for CVE-2026-73314 (1)

Exploits & Public PoCs for CVE-2026-73314 (1)

Security Blog Posts for CVE-2026-73314 (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-2026-73316 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-2026-73309 7.4 HIGH XenForo < 2.3.13 Authentication Bypass via OAuth2 Token Endpoint
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-754

V. Comments for CVE-2026-73314

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