CVE-2016-0799 in OpenSSL
Summary
by MITRE
The fmtstr function in crypto/bio/b_print.c in OpenSSL 1.0.1 before 1.0.1s and 1.0.2 before 1.0.2g improperly calculates string lengths, which allows remote attackers to cause a denial of service (overflow and out-of-bounds read) or possibly have unspecified other impact via a long string, as demonstrated by a large amount of ASN.1 data, a different vulnerability than CVE-2016-2842.
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Analysis
by VulDB Data Team • 07/08/2022
The vulnerability identified as CVE-2016-0799 represents a critical buffer handling flaw within the OpenSSL cryptographic library that affects versions prior to 1.0.1s and 1.0.2g. This issue resides in the fmtstr function located in the crypto/bio/b_print.c file, which is responsible for formatting and printing string data within the SSL/TLS implementation. The flaw stems from improper calculation of string lengths during the formatting process, creating a scenario where maliciously crafted input can trigger unpredictable behavior in the affected software components.
The technical implementation of this vulnerability exploits a classic buffer overflow condition through improper string length handling. When the fmtstr function processes input strings, it fails to properly validate or calculate the actual length of formatted output, particularly when dealing with ASN.1 data structures that can contain exceptionally long strings. This miscalculation allows attackers to craft inputs that exceed the allocated buffer space, leading to memory corruption that manifests as either out-of-bounds read operations or overflow conditions. The vulnerability specifically impacts the ASN.1 parsing functionality within OpenSSL, which is fundamental to certificate processing and secure communication protocols.
The operational impact of CVE-2016-0799 extends beyond simple denial of service to potentially enable more sophisticated attacks depending on the system configuration and attack surface. Remote attackers can leverage this vulnerability to cause service disruption through controlled memory corruption, leading to application crashes or system instability. In certain configurations, the out-of-bounds memory access patterns could potentially be exploited to achieve arbitrary code execution or information disclosure, making this vulnerability particularly dangerous for systems handling sensitive cryptographic operations. The vulnerability affects a wide range of applications relying on OpenSSL for secure communications, including web servers, email systems, and network infrastructure components.
From a cybersecurity perspective, this vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and relates to ATT&CK technique T1059 for command and control communication. The flaw demonstrates how seemingly minor implementation errors in cryptographic libraries can create significant security risks, particularly when these libraries form the foundation of internet security infrastructure. Organizations should prioritize immediate patching of affected OpenSSL versions to prevent exploitation, while implementing network monitoring to detect potential exploitation attempts. The vulnerability also underscores the importance of thorough input validation and bounds checking in cryptographic implementations, as highlighted in industry best practices for secure coding standards.
Mitigation strategies for CVE-2016-0799 require immediate deployment of patched OpenSSL versions, specifically upgrading to 1.0.1s or 1.0.2g and later releases. System administrators should conduct comprehensive inventory assessments to identify all systems running vulnerable OpenSSL versions and implement remediation plans accordingly. Network segmentation and access controls should be enhanced to limit exposure of vulnerable services, while intrusion detection systems should be configured to monitor for anomalous ASN.1 data patterns that might indicate exploitation attempts. Regular security assessments and vulnerability scanning should be implemented to identify similar issues in other cryptographic libraries and system components, as this vulnerability demonstrates how subtle coding errors can create significant security risks across the entire security infrastructure ecosystem.