CVE-2026-73311

XenForo before 2.3.13 contains an OAuth2 authorization code reuse vulnerability that allows attackers to obtain unauthorized token pairs by submitting a previously used authorization code. Attackers can exploit the failure to invalidate or mark authorization codes as consumed after initial token issuance to receive an independent token pair for the same user and scopes, bypassing the single-use guarantee of the OAuth2 authorization code flow.

• CWE-294

• https://bombobombone.github.io/posts/cve-2026-73311/Exploit, Third Party Advisory
• https://github.com/BomboBombone/CVE-2026-73311Exploit, Third Party Advisory
• https://www.vulncheck.com/advisories/xenforo-oauth2-authorization-code-reuseThird Party Advisory
• https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/Release Notes
• https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/Release Notes

Published

Sep 8, 2026

Last Modified

Sep 11, 2026

Status

Analyzed

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
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