CVE-2026-73309: XenForo < 2.3.13 Authentication Bypass via OAuth2 Token Endpoint
Fixed in 2.3.13 · Affected: XenForo before 2.3.13 · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 53% of scored CVEs
DescriptionCVE.org
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.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- XenForo · XenForobefore 2.3.13
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Vendor
- XenForo
- Published
- September 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-73309 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.