Is CVE-2026-73314 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-73314 being exploited in the wild.

How severe is CVE-2026-73314?

High severity, with a CVSS score of 7.5, published 8 September 2026.

Is there a fix for CVE-2026-73314?

A patch was published on 2026-09-08: XenForo 2.3.13 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-73314 attacked?

It is attacked over the network, in a web application.

Am I affected by CVE-2026-73314?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-73314: XenForo PayPal webhook signature verification bypass

CVE-2026-73314 · Severity: high · CVSS 7.5 · Published 2026-09-08

XenForo is a popular online community platform that processes payments through PayPal integration. This vulnerability allows attackers to forge PayPal payment notifications to extend user subscriptions without paying. A buyer with an active subscription could submit fake payment confirmations and extend their access indefinitely, bypassing PayPal's cryptographic signature verification that normally protects against this attack.

Quick answers

Is CVE-2026-73314 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-73314 being exploited in the wild.
How severe is CVE-2026-73314?: High severity, with a CVSS score of 7.5, published 8 September 2026.
Which products and versions are affected?: XenForo XenForo before 2.3.13.
Is there a fix for CVE-2026-73314?: A patch was published on 2026-09-08: XenForo 2.3.13 released Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-73314 attacked?: It is attacked over the network, in a web application.
Am I affected by CVE-2026-73314?: Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is a signature verification logic error in XenForo's PayPal REST webhook handler (PayPalRest::verifyWebhookSignature()). When a webhook arrives with an unsupported PAYPAL-AUTH-ALGO header value, the code fails to map it to a supported hash function, leaving the algorithm variable unset. Instead of rejecting the request, the verification function logs that the algorithm is unavailable and incorrectly returns true, causing the webhook processor to treat the unverified request as legitimate. An unauthenticated attacker with knowledge of an active recurring upgrade (available through the upgrade management UI) can craft a forged PAYMENT.CAPTURE.COMPLETED callback with an arbitrary unsupported algorithm header and the correct purchase key to extend the subscription without a valid PayPal signature. The fix in XenForo 2.3.13 explicitly rejects unsupported algorithms instead of treating them as successful verification.

Affected products

XenForo XenForo before 2.3.13

Timeline

2026-09-08: disclosed
2026-09-08: patched: XenForo 2.3.13 released

References

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