CVEvulnerability

CVE-2026-73309

9.1 CRITICAL Published 2026-09-08 Modified 2026-09-11 Official page ↗
Status
Analyzed
Published
2026-09-08
Last modified
2026-09-11
Assigner
[email protected]
CVSS 4.0 ([email protected])
9.1 CRITICAL — CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS 3.1 ([email protected])
7.4 HIGH — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS 3.1 ([email protected])
9.1 CRITICAL — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Weaknesses
CWE-697

Description

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 configurations

• xenforo xenforo (< 2.3.13)

Related

Weakness · CWE (1)

  • CWE-697 Incorrect Comparison weakness

References