CVE-2013-1623 in CyaSSL
Summary
by MITRE
The TLS and DTLS implementations in wolfSSL CyaSSL before 2.5.0 do not properly consider timing side-channel attacks on a noncompliant MAC check operation during the processing of malformed CBC padding, which allows remote attackers to conduct distinguishing attacks and plaintext-recovery attacks via statistical analysis of timing data for crafted packets, a related issue to CVE-2013-0169.
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Analysis
by VulDB Data Team • 12/29/2021
The vulnerability described in CVE-2013-1623 affects the TLS and DTLS implementations within wolfSSL CyaSSL cryptographic library versions prior to 2.5.0. This represents a significant security flaw that undermines the integrity of encrypted communications by exploiting timing side-channel vulnerabilities during the processing of malformed CBC padding. The issue stems from improper handling of MAC check operations that creates measurable timing differences between valid and invalid padding scenarios, making the cryptographic implementation susceptible to sophisticated attack vectors.
The technical flaw manifests in the way the cryptographic library processes CBC (Cipher Block Chaining) padding validation during TLS/DTLS protocol operations. When malformed padding is encountered, the implementation exhibits different processing times depending on whether the padding is valid or invalid, creating a timing side-channel that attackers can exploit. This timing variation occurs during the MAC (Message Authentication Code) verification process, where the library performs different computational paths for valid versus invalid padding, resulting in measurable differences in execution time that can be statistically analyzed by an attacker.
This vulnerability enables remote attackers to conduct distinguishing attacks and plaintext-recovery attacks through careful statistical analysis of timing data collected from crafted packets. The attack methodology leverages the timing differences to distinguish between valid and invalid padding, ultimately allowing adversaries to recover plaintext information from encrypted communications without possessing the cryptographic keys. The flaw is particularly dangerous because it operates at the protocol level during normal cryptographic operations, making it difficult to detect and prevent through conventional security measures.
The operational impact of this vulnerability extends beyond simple information disclosure, as it fundamentally compromises the confidentiality assurances provided by TLS and DTLS protocols. Systems utilizing affected versions of wolfSSL CyaSSL become vulnerable to sophisticated attacks that can gradually reconstruct sensitive data from encrypted traffic, potentially exposing authentication credentials, personal information, and proprietary data. The vulnerability affects a wide range of applications that rely on wolfSSL for secure communications, including embedded systems, IoT devices, and networked applications where the library is commonly deployed.
This vulnerability aligns with CWE-310, which addresses cryptographic issues related to timing side channels, and represents a specific implementation weakness that violates the principle of constant-time execution in cryptographic operations. The attack vector corresponds to techniques documented in the ATT&CK framework under T1552.004 for unsecured credentials and T1041 for data exfiltration through network communications. Organizations should immediately upgrade to wolfSSL version 2.5.0 or later to address this vulnerability, as the implementation includes proper constant-time MAC verification mechanisms that eliminate the timing side-channel attack surface. Additionally, network administrators should monitor for unusual timing patterns in encrypted traffic that might indicate exploitation attempts, and consider implementing additional security controls such as intrusion detection systems to detect potential timing-based attacks against cryptographic implementations.