CVE-2026-73311 XenForo < 2.3.13 OAuth2 Authorization Code Reuse
Attackers can reuse OAuth2 authorization codes to obtain unauthorized access tokens, bypassing single-use restrictions and potentially taking over user accounts.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-73311?
CVE-2026-73311 is a critical authentication bypass vulnerability in XenForo, published on 8 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-294
Which versions are affected by CVE-2026-73311?
It affects 1 product.
Products include Xenforo Xenforo.
How do I fix CVE-2026-73311?
No fix has been published for CVE-2026-73311 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-73311 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73311 exists.
Public exploit code: 1 proofs of concept on GitHub.
Other vulnerabilities in XenForo
Sources
Also known as GHSA-mrq5-6m75-wpj5.