CVE-2026-73309XenForo < 2.3.13 Authentication Bypass via OAuth2 Token Endpoint
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No exploitation reported and no EPSS estimate yet.
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XenForo before 2.3.13 contains an authentication bypass vulnerability in the OAuth2 token endpoint that allows unauthenticated attackers to obtain valid token pairs by submitting empty values for client_secret and code_verifier parameters. Attackers can exploit PHP truthy evaluation logic, which treats empty strings as false and skips client secret validation and PKCE code verifier validation, to exchange a valid authorization code for a token pair without proving client identity or holding the PKCE commitment.
- CVSS
- 7.4 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- Weakness (CWE)
- CWE-697
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- VulnCheck
- NVD analysis
- Analyzed
- Record last updated
- Oct 1, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
XenForo XenForo xenforo:xenforo (from the name) | before 2.3.13 | CNA record |
xenforo xenforo xenforo:xenforo | before 2.3.13 | NVD |
References
- https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-gallery-versions-2-2-0-2-3-12.239856/vendor-advisory, patch, release-notes
- https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-security-fixes.239857/release-notes
- https://bombobombone.github.io/posts/cve-2026-73309/technical-description, exploit, third-party-advisory
- https://github.com/BomboBombone/CVE-2026-73309exploit, third-party-advisory
- https://www.vulncheck.com/advisories/xenforo-authentication-bypass-via-oauth2-token-endpointthird-party-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.