Input validation error in authentik - CVE-2023-36456
Published: July 6, 2023 / Updated: April 23, 2026
Vulnerability identifier: #VU127143
CSH Severity: High
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:U/U:Amber
CVE-ID: CVE-2023-36456
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
authentik
authentik
Software vendor:
Authentik Security Inc
Authentik Security Inc
Description
The vulnerability allows a remote attacker to spoof IP addresses in logs, bypass IP-based policy checks, and influence IP-based controls in proxied applications.
The vulnerability exists due to improper input validation in X-Forwarded-For and X-Real-IP header handling in authentik when processing requests with user-supplied proxy IP headers. A remote attacker can send requests with crafted X-Forwarded-For or X-Real-IP headers to spoof IP addresses in logs, bypass IP-based policy checks, and influence IP-based controls in proxied applications.
Only deployments that are directly accessible by users without a reverse proxy are vulnerable.
Remediation
Install security update from vendor's website.