CVE-2013-4353 in OpenSSL
Summary
by MITRE
The ssl3_take_mac function in ssl/s3_both.c in OpenSSL 1.0.1 before 1.0.1f allows remote TLS servers to cause a denial of service (NULL pointer dereference and application crash) via a crafted Next Protocol Negotiation record in a TLS handshake.
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Analysis
by VulDB Data Team • 06/04/2021
The vulnerability identified as CVE-2013-4353 represents a critical denial of service flaw within the OpenSSL cryptographic library version 1.0.1 prior to 1.0.1f. This vulnerability specifically affects the ssl3_take_mac function located in the ssl/s3_both.c file, which is responsible for processing TLS handshake records. The issue manifests when remote TLS servers craft malicious Next Protocol Negotiation records that exploit a NULL pointer dereference during the SSL/TLS handshake process. This flaw operates at the protocol level and affects the secure communication infrastructure that billions of devices rely upon for encrypted data transmission.
The technical exploitation of this vulnerability occurs during the TLS handshake phase when the OpenSSL implementation processes Next Protocol Negotiation (NPN) extensions. The ssl3_take_mac function fails to properly validate or handle malformed NPN records, leading to a scenario where a NULL pointer is dereferenced during the MAC (Message Authentication Code) calculation process. This NULL pointer dereference results in an application crash and complete denial of service for the affected TLS server. The vulnerability is particularly dangerous because it can be triggered by any remote TLS server that initiates a handshake with the vulnerable OpenSSL implementation, making it a significant threat to web servers, email servers, and any service relying on TLS encryption.
From an operational perspective, this vulnerability poses severe risks to organizations maintaining TLS services as it allows attackers to remotely crash services without requiring authentication or special privileges. The impact extends beyond simple service disruption to potentially affect business continuity and availability of critical services. The vulnerability affects the broader TLS ecosystem since it impacts the fundamental handshake mechanism that establishes secure connections. This flaw exemplifies a classic buffer overflow or improper input validation issue that has been classified under CWE-476 as NULL Pointer Dereference, representing a fundamental weakness in input validation and memory management practices within cryptographic libraries.
The attack surface for CVE-2013-4353 is extensive given that OpenSSL is integrated into numerous operating systems, web servers, email servers, and network appliances that utilize TLS for secure communication. Organizations running vulnerable versions of OpenSSL are exposed to potential denial of service attacks that can render their services unavailable to legitimate users. The vulnerability aligns with ATT&CK technique T1499.004 which involves network denial of service attacks targeting TLS services. This vulnerability demonstrates the importance of proper input validation and error handling in cryptographic implementations, as the lack of proper boundary checks in the ssl3_take_mac function leads to predictable application crashes. The remediation process requires immediate patching of OpenSSL installations to version 1.0.1f or later, along with comprehensive testing to ensure that the patched implementations maintain proper TLS functionality while eliminating the NULL pointer dereference condition.
Organizations should implement network monitoring to detect unusual TLS handshake patterns that might indicate exploitation attempts, while also ensuring that all systems utilizing OpenSSL are updated to patched versions. The vulnerability highlights the critical need for regular security updates and proper vulnerability management processes within enterprise environments. Additionally, implementing proper input sanitization and validation practices in cryptographic library implementations can prevent similar issues from occurring in future deployments. This vulnerability serves as a reminder of the critical importance of thorough testing and validation of cryptographic implementations, particularly in widely deployed libraries that form the foundation of internet security infrastructure.