CVE-2009-0051 in ZXID
Summary
by MITRE
ZXID 0.29 and earlier does not properly check the return value from the OpenSSL DSA_verify function, which allows remote attackers to bypass validation of the certificate chain via a malformed SSL/TLS signature, a similar vulnerability to CVE-2008-5077.
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Analysis
by VulDB Data Team • 08/25/2019
The vulnerability identified as CVE-2009-0051 affects ZXID versions 0.29 and earlier, representing a critical flaw in the cryptographic validation process of SSL/TLS certificate chains. This issue stems from improper handling of return values from the OpenSSL DSA_verify function, creating a significant security gap that adversaries can exploit to bypass essential certificate validation mechanisms. The flaw operates at the core of digital signature verification processes where the system fails to properly assess the integrity of cryptographic signatures, potentially allowing malicious actors to present fraudulent certificates that appear valid to the system.
The technical implementation of this vulnerability resides in the certificate validation logic where ZXID relies on OpenSSL's DSA_verify function to authenticate digital signatures within SSL/TLS certificates. When this function returns a value indicating signature verification failure, the ZXID software does not properly process this return code, instead continuing to accept potentially invalid signatures. This misimplementation creates a scenario where attackers can craft malformed SSL/TLS signatures that pass validation checks despite being cryptographically invalid. The vulnerability demonstrates a classic weakness in error handling and input validation, aligning with CWE-252, which addresses "Unchecked Return Values" in security-critical functions.
From an operational perspective, this vulnerability enables remote attackers to perform man-in-the-middle attacks by presenting forged certificates that appear legitimate to the vulnerable ZXID system. The impact extends beyond simple certificate validation bypass, as it undermines the fundamental trust model of SSL/TLS communications. An attacker could potentially intercept and modify encrypted traffic between clients and servers, compromising the confidentiality and integrity of sensitive data exchanges. The vulnerability is particularly dangerous because it operates silently, allowing malicious activities to proceed undetected while the system continues to trust invalid certificates.
The security implications of CVE-2009-0051 align with techniques described in the MITRE ATT&CK framework under the T1573.001 tactic for "Encrypted Channel" and T1071.001 for "Application Layer Protocol". This vulnerability allows attackers to establish fraudulent secure connections that bypass traditional security controls, making it particularly challenging to detect through conventional network monitoring. The flaw also relates to the broader category of cryptographic weaknesses that can be exploited to undermine the security of encrypted communications, similar to the approach used in CVE-2008-5077 which this vulnerability mirrors in its exploitation methodology.
Mitigation strategies for this vulnerability require immediate patching of affected ZXID installations to versions that properly handle OpenSSL function return values. Organizations should implement comprehensive certificate monitoring to detect and respond to potentially compromised certificates, while also strengthening their overall certificate management processes. The fix involves ensuring that all return values from OpenSSL cryptographic functions are properly validated before proceeding with certificate acceptance, implementing proper error handling that terminates validation processes when signature verification fails. Additionally, network administrators should consider implementing certificate pinning mechanisms and regular security assessments to prevent exploitation of similar vulnerabilities in other cryptographic components.