CVE-2019-9498 in hostapd
Summary
by MITRE
The implementations of EAP-PWD in hostapd EAP Server, when built against a crypto library missing explicit validation on imported elements, do not validate the scalar and element values in EAP-pwd-Commit. An attacker may be able to use invalid scalar/element values to complete authentication, gaining session key and network access without needing or learning the password. Both hostapd with SAE support and wpa_supplicant with SAE support prior to and including version 2.4 are affected. Both hostapd with EAP-pwd support and wpa_supplicant with EAP-pwd support prior to and including version 2.7 are affected.
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Analysis
by VulDB Data Team • 08/29/2023
The vulnerability identified as CVE-2019-9498 represents a critical flaw in the EAP-PWD authentication implementation within hostapd and wpa_supplicant wireless authentication frameworks. This weakness specifically affects systems utilizing the EAP-PWD (Extensible Authentication Protocol - Password) method, which is designed to provide secure password-based authentication for wireless networks. The vulnerability stems from insufficient validation of cryptographic parameters during the EAP-pwd-Commit phase of the authentication process, creating a pathway for attackers to bypass legitimate authentication requirements.
The technical flaw manifests when hostapd or wpa_supplicant is compiled against cryptographic libraries that fail to perform explicit validation on imported scalar and element values. During the EAP-PWD authentication handshake, the protocol exchanges commitment messages containing cryptographic parameters that must be validated to ensure their mathematical correctness and security properties. The absence of proper validation allows attackers to inject malformed scalar values and element parameters that would normally be rejected by cryptographic libraries implementing strict validation. This validation failure occurs specifically in the EAP-pwd-Commit message processing, where the system accepts invalid cryptographic parameters without sufficient verification.
The operational impact of this vulnerability is severe as it enables attackers to complete the authentication process without knowledge of the actual network password. When an attacker successfully exploits this weakness, they can establish a valid session key and gain full network access to the wireless infrastructure. This represents a fundamental breakdown in the authentication security model, as the attacker essentially gains the same privileges as a legitimate user who knows the correct password. The vulnerability affects multiple versions of both hostapd and wpa_supplicant, with the issue persisting in all versions up to and including 2.4 for SAE support and 2.7 for EAP-pwd support, indicating a prolonged period of exposure.
The security implications extend beyond simple unauthorized access to encompass potential man-in-the-middle attacks and credential compromise scenarios. This vulnerability directly relates to CWE-295, which addresses improper certificate validation, and aligns with ATT&CK technique T1566, representing the exploitation of credential validation weaknesses. The flaw enables attackers to perform authentication bypass attacks without requiring the knowledge of the password, effectively nullifying the password-based security mechanism. Organizations using affected wireless infrastructure face significant risk of unauthorized network access and potential data breaches, as the vulnerability allows attackers to establish persistent network presence without detection.
Mitigation strategies should focus on immediate software updates to versions that address the validation deficiency in cryptographic parameter handling. Network administrators must ensure all hostapd and wpa_supplicant implementations are upgraded to versions that include proper validation of scalar and element values in EAP-pwd-Commit messages. Additionally, organizations should implement network monitoring to detect unusual authentication patterns that might indicate exploitation attempts. The fix typically involves adding explicit validation checks for cryptographic parameters during the EAP-PWD authentication process, ensuring that all imported scalar values and element parameters meet the required mathematical properties before acceptance. Security teams should also consider implementing additional authentication layers and network segmentation to reduce the potential impact of successful exploitation attempts.