CVE-2026-73309
criticalXenForo before 2.3.13 contains an authentication bypass vulnerability in the OAuth2 token endpoint that allows unauthenticated attackers to obtain valid token…
Vendor / product: Xenforo — xenforo
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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N Affected products
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
No vendor advisory or patch reference tagged by NVD. Check the references below.
References
- https://bombobombone.github.io/posts/cve-2026-73309/ disclosure@vulncheck.com
- https://github.com/BomboBombone/CVE-2026-73309 disclosure@vulncheck.com
- https://www.vulncheck.com/advisories/xenforo-authentication-bypass-via-oauth2-token-endpoi... disclosure@vulncheck.com
- https://xenforo.com/community/threads/security-fixes-released-for-all-xenforo-and-media-ga... disclosure@vulncheck.com
- https://xenforo.com/community/threads/xenforo-2-3-13-and-add-ons-released-includes-securit... disclosure@vulncheck.com