Vulnerability in Xenforo
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.
CVSS v3 metric
CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
Affected products
Weakness classification (CWE)
Public proof-of-concept exploits
References
- disclosure@vulncheck.com (vendor-advisory, patch)
- disclosure@vulncheck.com (release-notes)
- disclosure@vulncheck.com (third-party-advisory)
- disclosure@vulncheck.com (technical-description)
- disclosure@vulncheck.com (exploit)
Frequently asked questions
- What is CVE-2026-73311?
- CVE-2026-73311 is a high-severity vulnerability in Xenforo, classified under Authentication Bypass by Capture-replay. CVSS score: 7.4/10. Published 2026-09-08.
- How severe is CVE-2026-73311?
- High severity. CVSS v3 base score is 7.4 out of 10.
- Is CVE-2026-73311 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.