CVE-2020-35733 in OTP
Summary
by MITRE • 01/16/2021
An issue was discovered in Erlang/OTP before 23.2.2. The ssl application 10.2 accepts and trusts an invalid X.509 certificate chain to a trusted root Certification Authority.
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Analysis
by VulDB Data Team • 02/14/2021
The vulnerability identified as CVE-2020-35733 represents a critical certificate validation flaw within the Erlang/OTP ssl application version 10.2 and earlier. This issue affects systems that rely on Erlang's cryptographic libraries for secure communications, particularly those implementing ssl protocols for network security. The flaw stems from improper certificate chain validation mechanisms that allow malicious actors to present invalid X.509 certificates while still maintaining trust in the connection. This vulnerability directly impacts the fundamental security guarantees that X.509 certificates provide in public key infrastructure implementations. The ssl application in affected Erlang versions fails to properly verify certificate chains against established trust anchors, creating a pathway for man-in-the-middle attacks and unauthorized system access. Organizations utilizing Erlang-based applications for secure communications face significant risks when this vulnerability remains unaddressed.
The technical root cause of this vulnerability lies in the ssl application's certificate validation logic that does not adequately enforce certificate chain integrity checks. Specifically, the implementation accepts certificate chains that should be rejected based on established X.509 validation criteria, including proper certificate path validation, signature verification, and trust anchor alignment. This flaw allows attackers to construct certificate chains that appear legitimate but contain invalid intermediate certificates or malformed trust relationships. The vulnerability manifests when the ssl application processes certificate chains without performing comprehensive validation of certificate attributes, including subject alternative names, certificate validity periods, and proper certificate authority relationships. This type of flaw typically maps to CWE-295 which specifically addresses improper certificate validation and trust chain verification. The weakness enables attackers to bypass critical security controls that should prevent the establishment of secure connections with untrusted certificates.
The operational impact of CVE-2020-35733 extends beyond simple certificate validation failures to encompass broader security implications for Erlang-based systems. Any application that utilizes Erlang's ssl capabilities for secure communications becomes vulnerable to certificate spoofing attacks, potentially allowing attackers to establish secure connections with malicious servers or intercept communications between legitimate parties. This vulnerability affects systems implementing secure protocols such as https, ftps, smtps, and other ssl/tls based services running on Erlang platforms. The impact is particularly severe for applications that rely on certificate-based authentication mechanisms, as attackers can exploit this weakness to impersonate legitimate services or gain unauthorized access to protected resources. Organizations may experience data breaches, unauthorized access to sensitive information, and complete compromise of secure communication channels. The vulnerability also affects systems that depend on certificate pinning or other certificate-based trust mechanisms, potentially undermining entire security architectures built on certificate validation.
Mitigation of this vulnerability requires immediate patching of affected Erlang/OTP installations to version 23.2.2 or later where the ssl application properly validates certificate chains. Organizations should conduct comprehensive vulnerability assessments to identify all systems running affected Erlang versions and ensure proper patch management procedures are in place. Security teams should implement monitoring for unusual certificate validation behaviors and establish automated alerting for potential certificate chain validation failures. Additionally, organizations may need to consider implementing additional security controls such as certificate pinning, certificate transparency monitoring, and enhanced network segmentation to reduce the attack surface. The remediation process should include thorough testing of patched systems to ensure that legitimate certificate chains continue to function properly while invalid chains are properly rejected. Security teams should also review their certificate management practices and ensure that proper certificate lifecycle management procedures are followed to prevent similar vulnerabilities from emerging in the future. This vulnerability highlights the critical importance of proper cryptographic implementation and validation in security-critical systems, aligning with ATT&CK technique T1552.001 for credential access through certificate manipulation and T1046 for network service scanning that may reveal vulnerable systems.