CVE-2015-1789 in SPARC Enterprise Server
Summary
by MITRE
The X509_cmp_time function in crypto/x509/x509_vfy.c in OpenSSL before 0.9.8zg, 1.0.0 before 1.0.0s, 1.0.1 before 1.0.1n, and 1.0.2 before 1.0.2b allows remote attackers to cause a denial of service (out-of-bounds read and application crash) via a crafted length field in ASN1_TIME data, as demonstrated by an attack against a server that supports client authentication with a custom verification callback.
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Analysis
by VulDB Data Team • 07/26/2022
The vulnerability identified as CVE-2015-1789 represents a critical out-of-bounds read condition within the OpenSSL cryptographic library that affects multiple version branches including 0.9.8, 1.0.0, 1.0.1, and 1.0.2 series. This flaw exists in the X509_cmp_time function located in the crypto/x509/x509_vfy.c source file, which is responsible for comparing time values in X.509 certificates during certificate verification processes. The vulnerability manifests when the function processes ASN1_TIME data structures containing crafted length fields that exceed expected boundaries, leading to memory access violations that can be exploited remotely.
The technical implementation of this vulnerability stems from insufficient input validation within the certificate verification pipeline. When OpenSSL encounters a certificate with malformed ASN1_TIME data, the X509_cmp_time function fails to properly bounds-check the length field before attempting to read memory locations beyond the allocated buffer boundaries. This particular flaw falls under CWE-129, which specifically addresses insufficient validation of length fields, and represents a classic example of improper input validation that can lead to memory corruption vulnerabilities. The function's failure to validate the integrity of the ASN1_TIME structure's length field creates a scenario where an attacker can manipulate the parsing logic to access memory outside the intended data structure, potentially causing application crashes or more severe memory corruption issues.
The operational impact of CVE-2015-1789 extends beyond simple denial of service conditions, as it can be leveraged by remote attackers to disrupt certificate validation processes in SSL/TLS implementations. Servers configured to perform client certificate authentication become particularly vulnerable since they must process client-provided certificates containing potentially malicious time fields. This vulnerability can be exploited as part of broader attack vectors within the MITRE ATT&CK framework, specifically under the T1071.004 technique for application layer protocol traffic shaping and potentially the T1499.004 technique for network disruption. The attack scenario typically involves an attacker establishing a TLS connection to a vulnerable server, presenting a malicious client certificate with crafted ASN1_TIME data, and triggering the out-of-bounds read condition that results in application instability or complete crash.
Mitigation strategies for CVE-2015-1789 primarily focus on immediate version upgrades to patched OpenSSL releases, with affected versions requiring updates to 0.9.8zg, 1.0.0s, 1.0.1n, or 1.0.2b respectively. Organizations should also implement network-level monitoring to detect unusual certificate validation patterns and consider deploying intrusion detection systems that can identify malformed ASN1_TIME structures in certificate data. The vulnerability highlights the importance of robust input validation in cryptographic libraries and demonstrates how seemingly benign certificate parsing operations can become attack vectors when proper bounds checking is absent. Security teams should also review custom certificate verification callbacks to ensure they properly handle edge cases and do not inadvertently expose the system to additional attack surfaces through improper error handling or validation logic.
This vulnerability serves as a critical reminder of the security implications inherent in cryptographic library implementations, where memory safety issues can have far-reaching consequences for SSL/TLS security. The flaw's existence across multiple OpenSSL branches demonstrates the importance of comprehensive security testing and validation of cryptographic components, particularly those handling certificate data processing. Organizations should also consider implementing certificate pinning strategies and additional verification layers to reduce the attack surface when dealing with client certificate authentication scenarios that may be vulnerable to this type of manipulation.