CVE-2022-23304: W1.fi Hostapd Information Disclosure Bug

CVE-2022-23304 Overview

CVE-2022-23304 is a critical side-channel vulnerability affecting the implementations of EAP-pwd in hostapd before version 2.10 and wpa_supplicant before version 2.10. The vulnerability arises from observable cache access patterns during cryptographic operations, which can be exploited by attackers to extract sensitive authentication credentials. Notably, this issue exists because of an incomplete fix for CVE-2019-9495, indicating that previous remediation efforts failed to fully address the underlying security weakness.

Critical Impact

Successful exploitation allows network-based attackers to compromise wireless authentication credentials through cache timing analysis, potentially enabling unauthorized network access, man-in-the-middle attacks, and complete compromise of affected wireless networks.

Affected Products

• w1.fi hostapd (versions prior to 2.10)
• w1.fi wpa_supplicant (versions prior to 2.10)
• Fedora Project Fedora 35

Discovery Timeline

• 2022-01-17 - CVE-2022-23304 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2022-23304

Vulnerability Analysis

The vulnerability exists within the EAP-pwd (Extensible Authentication Protocol - Password) implementation used in hostapd and wpa_supplicant. EAP-pwd is a password-based authentication protocol commonly deployed in enterprise wireless networks (WPA2-Enterprise and WPA3-Enterprise configurations). The flaw stems from non-constant-time cryptographic operations that create observable cache access patterns during the password-to-element mapping process.

When processing EAP-pwd authentication exchanges, the affected implementations perform cryptographic operations whose execution time and memory access patterns vary based on the secret values being processed. An attacker positioned on the same physical hardware or within the same virtualized environment can monitor CPU cache behavior to infer sensitive cryptographic material, including password-derived secrets used in the authentication process.

This vulnerability is particularly significant as it represents an incomplete fix for CVE-2019-9495, which addressed similar side-channel concerns. The persistence of exploitable cache timing patterns after the previous remediation demonstrates the difficulty of fully eliminating side-channel leakage from cryptographic implementations.

Root Cause

The root cause is classified as CWE-203: Observable Discrepancy. The EAP-pwd implementation uses cryptographic operations that exhibit variable timing characteristics based on secret-dependent conditional branches and memory access patterns. Specifically, the password-to-element (PWE) derivation process does not employ constant-time algorithms, allowing attackers to distinguish between different execution paths by observing cache hit/miss patterns. The incomplete fix from CVE-2019-9495 failed to address all code paths where secret-dependent branching occurs.

Attack Vector

The attack exploits cache-based side-channel leakage during EAP-pwd authentication. An attacker with local access to the same CPU (through co-location on shared hardware, virtual machine co-residency, or malicious processes on the target system) can perform cache timing analysis to extract information about the password being used for authentication.

The attack methodology involves:

1. The attacker monitors CPU cache state while the victim performs EAP-pwd authentication
2. By observing which cache lines are accessed during cryptographic operations, the attacker can infer secret-dependent branching decisions
3. Statistical analysis of multiple authentication attempts allows recovery of password material
4. With sufficient observations, the attacker can reconstruct the password or derive equivalent authentication credentials

Since this is a network-accessible service, the attack can be combined with techniques to trigger repeated authentication attempts, increasing the attacker's ability to gather timing samples.

Detection Methods for CVE-2022-23304

Indicators of Compromise

• Unusual patterns of failed or repeated EAP-pwd authentication attempts from legitimate clients
• Presence of unauthorized processes with elevated privileges monitoring CPU cache states
• Unexpected co-resident virtual machines or containers on systems running hostapd or wpa_supplicant
• Evidence of cache-timing attack tools (such as Flush+Reload or Prime+Probe implementations) on affected systems

Detection Strategies

• Monitor authentication logs for anomalous EAP-pwd authentication patterns that may indicate timing attack data collection
• Implement endpoint detection to identify known cache side-channel attack tools and techniques
• Deploy version scanning to identify hostapd and wpa_supplicant installations running versions prior to 2.10
• Enable security auditing on systems running wireless authentication services to detect suspicious process behavior

Monitoring Recommendations

• Configure centralized logging for all wireless authentication events and correlate across multiple access points
• Implement performance monitoring to detect unusual CPU cache behavior patterns that may indicate active exploitation
• Establish baseline metrics for EAP-pwd authentication timing to identify statistical anomalies
• Monitor for security advisories from w1.fi and distribution vendors regarding additional patches or mitigations

How to Mitigate CVE-2022-23304

Immediate Actions Required

• Upgrade hostapd to version 2.10 or later immediately on all affected access points and authentication servers
• Upgrade wpa_supplicant to version 2.10 or later on all client systems using EAP-pwd authentication
• Consider temporarily disabling EAP-pwd authentication method in favor of certificate-based EAP methods (EAP-TLS) until patches are applied
• Audit wireless network configurations to identify all systems running vulnerable versions

Patch Information

The w1.fi project has released version 2.10 of both hostapd and wpa_supplicant which addresses this vulnerability. Users should update to version 2.10 or later to receive the complete fix. The official security advisory is available from WPA Supplicant Security Advisory.

Distribution-specific patches are available:

• Fedora users should apply updates per the Fedora Package Announcement
• Gentoo users should refer to Gentoo GLSA 202309-16
• Debian users should consult the Debian LTS Announcement April 2025

Workarounds

• Disable EAP-pwd authentication and use alternative EAP methods such as EAP-TLS with certificate-based authentication
• Implement network segmentation to isolate wireless authentication infrastructure from untrusted workloads
• On virtualized environments, ensure wireless authentication services run on dedicated physical hosts without untrusted co-residents
• Apply operating system-level mitigations for cache side-channel attacks where available (such as cache partitioning features)

# Configuration example - Disable EAP-pwd in hostapd.conf
# Remove or comment out EAP-pwd from supported methods
eap_server=1
eap_user_file=/etc/hostapd/eap_user
# Remove "pwd" from eap methods in eap_user_file
# Use EAP-TLS or EAP-PEAP instead