CVE-2019-11235 in FreeRADIUS
Summary
by MITRE
FreeRADIUS before 3.0.19 mishandles the "each participant verifies that the received scalar is within a range, and that the received group element is a valid point on the curve being used" protection mechanism, aka a "Dragonblood" issue, a similar issue to CVE-2019-9498 and CVE-2019-9499.
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Analysis
by VulDB Data Team • 06/01/2020
The CVE-2019-11235 vulnerability represents a critical cryptographic flaw in FreeRADIUS versions prior to 3.0.19 that directly impacts the security of EAP-TLS and EAP-TTLS authentication protocols. This vulnerability stems from inadequate implementation of cryptographic validation mechanisms within the elliptic curve cryptography (ECC) operations used during the authentication process. The flaw specifically affects the Dragonblood attack vector, which exploits weaknesses in how cryptographic parameters are validated during key exchange operations. The vulnerability is particularly concerning because it undermines the fundamental security guarantees that elliptic curve cryptography is designed to provide, potentially allowing attackers to bypass critical authentication controls.
The technical implementation flaw manifests in the failure to properly validate elliptic curve group elements and scalar values received during the cryptographic handshake process. According to CWE-310, this represents a weakness in cryptographic key generation and validation, where the system fails to verify that received cryptographic parameters conform to expected mathematical properties. The vulnerability allows an attacker to manipulate the cryptographic parameters in such a way that they can create valid-looking authentication exchanges while actually compromising the security of the underlying key exchange mechanism. This is particularly dangerous because the system's validation logic fails to check that the received group elements are valid points on the elliptic curve, enabling what is known as a "curve validation attack" that can lead to full authentication bypass.
The operational impact of this vulnerability extends beyond simple authentication failures and can result in complete compromise of network access controls. Attackers exploiting this vulnerability can potentially gain unauthorized access to networks protected by FreeRADIUS servers, as the cryptographic protections designed to prevent man-in-the-middle attacks are effectively neutralized. The vulnerability affects organizations relying on EAP-TLS and EAP-TTLS implementations, which are commonly used in enterprise wireless networks, VPN access, and other scenarios requiring strong authentication. According to ATT&CK framework category T1550, this vulnerability enables credential access through exploitation of cryptographic weaknesses, potentially leading to lateral movement and persistent access within network environments. The impact is particularly severe because it affects the foundational security of the authentication infrastructure rather than just individual authentication attempts.
Organizations should immediately upgrade to FreeRADIUS version 3.0.19 or later to address this vulnerability, as the fix implements proper cryptographic parameter validation and curve point verification. Additional mitigations include implementing network segmentation to limit the impact of potential exploitation, monitoring authentication logs for unusual patterns that might indicate attempted exploitation, and ensuring that all cryptographic parameters are validated against known good values. Security teams should also consider implementing additional layers of authentication and access control measures to provide defense-in-depth protection. The vulnerability demonstrates the critical importance of proper cryptographic implementation and validation, as highlighted by CWE-310's emphasis on ensuring that cryptographic operations maintain their security properties throughout the entire protocol execution. Organizations should conduct thorough security assessments of their authentication infrastructure to identify any other systems that might be similarly vulnerable to Dragonblood-style attacks.