CVE-2023-52160: Debian Linux Auth Bypass Vulnerability

CVE-2023-52160 Overview

CVE-2023-52160 is an authentication bypass vulnerability in the PEAP (Protected Extensible Authentication Protocol) implementation within wpa_supplicant through version 2.10. This vulnerability allows attackers to bypass authentication by exploiting a flaw in the eap_peap_decrypt function when wpa_supplicant is configured to not verify the network's TLS certificate during Phase 1 authentication. The attack enables adversaries to impersonate legitimate Enterprise Wi-Fi networks, potentially exposing users to malicious access points and network-based attacks.

Critical Impact

Attackers can impersonate Enterprise Wi-Fi networks by bypassing Phase 2 authentication, enabling man-in-the-middle attacks and unauthorized network access on affected Linux, Android, and ChromeOS devices.

Affected Products

• w1.fi wpa_supplicant through version 2.10
• Debian Linux 10.0
• Fedora 38 and 39
• Red Hat Enterprise Linux 8.0 and 9.0
• Google Android
• Google ChromeOS
• Linux Kernel (systems using wpa_supplicant)

Discovery Timeline

• 2024-02-22 - CVE-2023-52160 published to NVD
• 2025-11-04 - Last updated in NVD database

Technical Details for CVE-2023-52160

Vulnerability Analysis

The vulnerability resides in the PEAP authentication implementation within wpa_supplicant, specifically in how the eap_peap_decrypt function handles authentication phases. PEAP authentication normally consists of two phases: Phase 1 establishes a TLS tunnel, and Phase 2 performs the actual user authentication within that tunnel.

This vulnerability allows an attacker to completely skip Phase 2 authentication by sending an EAP-TLV Success packet prematurely. When wpa_supplicant is configured without TLS certificate verification for Phase 1 (a common misconfiguration in enterprise environments for ease of deployment), the client becomes susceptible to this attack.

The flaw is classified under CWE-287 (Improper Authentication), as it allows authentication mechanisms to be bypassed entirely. This is particularly dangerous in enterprise environments where users expect their Wi-Fi connections to be secure and authenticated.

Root Cause

The root cause is improper validation of the authentication state machine in the eap_peap_decrypt function. The code fails to verify that Phase 2 authentication has been properly completed before accepting an EAP-TLV Success packet. When TLS certificate validation is disabled during Phase 1, an attacker-controlled access point can send a premature success notification, causing the client to believe authentication is complete without ever performing Phase 2 credential verification.

Attack Vector

The attack requires the following conditions:

1. The target device must be running wpa_supplicant version 2.10 or earlier
2. wpa_supplicant must be configured without TLS certificate verification for Phase 1 authentication
3. The attacker must be within wireless range to set up a rogue access point

The attacker creates a malicious access point that mimics a legitimate Enterprise Wi-Fi network. When a victim device attempts to connect, the attacker's access point completes the Phase 1 TLS handshake (without proper certificate validation by the client) and then immediately sends an EAP-TLV Success packet instead of initiating Phase 2 authentication. The vulnerable wpa_supplicant accepts this packet and considers the connection authenticated, allowing the attacker to intercept all network traffic.

The attack is network-based and requires user interaction (the user must be in range of the rogue access point and their device must attempt to connect to the impersonated network).

Detection Methods for CVE-2023-52160

Indicators of Compromise

• Unexpected disconnections from known Enterprise Wi-Fi networks followed by automatic reconnection
• Authentication logs showing successful connections without proper Phase 2 authentication completion
• Detection of rogue access points with SSIDs matching legitimate enterprise networks
• Network traffic indicating connections to previously unknown RADIUS servers

Detection Strategies

• Monitor for anomalous EAP-TLV Success packets that occur immediately after Phase 1 without Phase 2 negotiation
• Implement wireless intrusion detection systems (WIDS) to identify rogue access points mimicking enterprise SSIDs
• Review wpa_supplicant configuration files for missing or disabled certificate validation (ca_cert parameter)
• Audit authentication logs on RADIUS servers for connections that bypass normal authentication flows

Monitoring Recommendations

• Deploy network monitoring to detect unauthorized access points broadcasting enterprise SSIDs
• Configure alerts for devices connecting to networks without proper certificate validation
• Implement centralized logging of all wireless authentication events for forensic analysis
• Use endpoint detection solutions to monitor wpa_supplicant configuration changes

How to Mitigate CVE-2023-52160

Immediate Actions Required

• Update wpa_supplicant to a patched version that includes the fix from commit 8e6485a1bcb0baffdea9e55255a81270b768439c
• Enable TLS certificate verification in wpa_supplicant configuration for all Phase 1 PEAP connections
• Configure the ca_cert parameter in wpa_supplicant to point to the appropriate CA certificate for your enterprise network
• Review and update network profiles on all managed devices to ensure proper certificate validation

Patch Information

The vulnerability has been addressed in the wpa_supplicant codebase. The fix is available in hostap commit 8e6485a1bcb0baffdea9e55255a81270b768439c. Major Linux distributions have released patches:

• Debian: Security update available via Debian LTS Security Announcement
• Fedora: Updates available for Fedora 38 and 39 via Fedora Package Announcements
• Red Hat Enterprise Linux: Updates available for RHEL 8.0 and 9.0

For Android and ChromeOS devices, check with Google for vendor-specific updates.

Workarounds

• Configure wpa_supplicant to always verify TLS certificates by setting the ca_cert parameter to a valid CA certificate path
• Use domain suffix matching with the domain_suffix_match parameter to validate server certificates
• Implement network access control policies that require certificate validation for all enterprise Wi-Fi connections
• Consider using alternative authentication methods such as EAP-TLS that provide mutual certificate authentication

# wpa_supplicant configuration to enable certificate validation
# Add to /etc/wpa_supplicant/wpa_supplicant.conf

network={
    ssid="EnterpriseWiFi"
    key_mgmt=WPA-EAP
    eap=PEAP
    identity="username"
    password="password"
    ca_cert="/etc/ssl/certs/enterprise-ca.pem"
    domain_suffix_match="enterprise.example.com"
    phase2="auth=MSCHAPV2"
}