XenForo up to 2.3.12 PayPal REST Payment Provider authentication replay

Summaryinfo

A vulnerability, which was classified as critical, has been found in XenForo up to 2.3.12. Affected is an unknown function of the component PayPal REST Payment Provider. The manipulation leads to authentication replay. This vulnerability is uniquely identified as CVE-2026-73316. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as critical, has been found in XenForo up to 2.3.12. This issue affects an unknown functionality of the component PayPal REST Payment Provider. The manipulation with an unknown input leads to a authentication replay vulnerability. Using CWE to declare the problem leads to CWE-294. A capture-replay flaw exists when the design of the product makes it possible for a malicious user to sniff network traffic and bypass authentication by replaying it to the server in question to the same effect as the original message (or with minor changes). Impacted is confidentiality, integrity, and availability. The summary by CVE is:

XenForo before 2.3.13 contains a payment replay vulnerability in the PayPal REST payment provider that allows attackers to process the same webhook payload multiple times by exploiting a missing duplicate transaction ID check. Attackers can replay a valid webhook payload to trigger duplicate payment events, resulting in repeated subscription activations and unauthorized account upgrades.

It is possible to read the advisory at xenforo.com. The identification of this vulnerability is CVE-2026-73316 since 08/11/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1040 according to MITRE ATT&CK.

Upgrading to version 2.3.13 eliminates this vulnerability.

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Productinfo

Name

• XenForo

Version

• 2.3.0
• 2.3.1
• 2.3.2
• 2.3.3
• 2.3.4
• 2.3.5
• 2.3.6
• 2.3.7
• 2.3.8
• 2.3.9
• 2.3.10
• 2.3.11
• 2.3.12

CPE 2.3info

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CPE 2.2info

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