CVE-2021-3336 in wolfSSL
Summary
by MITRE • 01/29/2021
DoTls13CertificateVerify in tls13.c in wolfSSL through 4.6.0 does not cease processing for certain anomalous peer behavior (sending an ED22519, ED448, ECC, or RSA signature without the corresponding certificate).
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Analysis
by VulDB Data Team • 02/21/2021
The vulnerability identified as CVE-2021-3336 resides within the wolfSSL library version 4.6.0 and earlier, specifically within the DoTls13CertificateVerify function located in the tls13.c file. This flaw represents a critical security issue that stems from inadequate validation of peer certificate signatures during the TLS 1.3 handshake process. The vulnerability manifests when a malicious peer attempts to send a signature using elliptic curve digital signature algorithm ed25519, ed448, elliptic curve cryptography, or rsa algorithms without providing the corresponding certificate that would normally validate the signature's authenticity.
The technical implementation flaw occurs because the DoTls13CertificateVerify function fails to properly validate that a signature corresponds to a valid certificate in the peer's certificate chain. This oversight creates a condition where an attacker can potentially bypass certificate verification mechanisms by submitting a signature without the associated certificate information, effectively allowing for authentication bypass scenarios. The vulnerability specifically targets the TLS 1.3 protocol implementation and affects the certificate verification process during the handshake phase, where the server validates the client's certificate signature.
From an operational impact perspective, this vulnerability enables attackers to exploit the certificate verification gap in TLS 1.3 implementations, potentially allowing for man-in-the-middle attacks or unauthorized access to protected resources. The flaw could be leveraged to impersonate legitimate clients or servers, undermining the fundamental security guarantees that TLS 1.3 is designed to provide. Attackers could exploit this by crafting malicious TLS handshakes that present valid signatures without proper certificate validation, thereby circumventing the expected authentication mechanisms. This vulnerability directly impacts the integrity and authenticity properties of TLS 1.3 connections.
The security implications of this vulnerability align with CWE-295 which addresses improper certificate validation, and can be mapped to ATT&CK technique T1573.001 for securing communications protocols. Organizations using wolfSSL versions prior to 4.6.1 should consider immediate remediation efforts, including upgrading to the patched version and implementing additional monitoring for anomalous certificate verification patterns. Network administrators should also consider implementing certificate pinning mechanisms and enhanced TLS inspection capabilities to detect and prevent exploitation attempts. The vulnerability demonstrates a critical gap in cryptographic library implementations where protocol compliance is not properly enforced during certificate verification processes.
This flaw represents a significant concern for systems relying on wolfSSL for secure communications, particularly those handling sensitive data or requiring strong authentication mechanisms. The vulnerability's impact extends beyond simple certificate validation issues to potentially compromise entire secure communication channels, making it essential for security teams to prioritize remediation efforts and conduct thorough vulnerability assessments of systems utilizing affected wolfSSL versions. The issue underscores the importance of comprehensive protocol validation in cryptographic implementations and highlights the need for robust certificate verification mechanisms in modern TLS implementations.