CVE-2016-7054 in OpenSSL
Summary
by MITRE
In OpenSSL 1.1.0 before 1.1.0c, TLS connections using *-CHACHA20-POLY1305 ciphersuites are susceptible to a DoS attack by corrupting larger payloads. This can result in an OpenSSL crash. This issue is not considered to be exploitable beyond a DoS.
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Analysis
by VulDB Data Team • 10/24/2024
The vulnerability described in CVE-2016-7054 affects OpenSSL versions 1.1.0 through 1.1.0b, specifically targeting TLS connections that utilize the CHACHA20-POLY1305 ciphersuites. This represents a denial of service weakness that arises from improper handling of large data payloads within the cryptographic processing pipeline. The flaw manifests when OpenSSL encounters corrupted data during the decryption process of TLS traffic using these particular cipher suites, leading to a crash condition that terminates the service. The vulnerability stems from insufficient input validation and error handling mechanisms within the TLS implementation, particularly in how the software processes the authenticated encryption operations that are fundamental to the CHACHA20-POLY1305 algorithm. This issue is classified under CWE-248, which addresses the exposure of an exception to an unexpected environment, and aligns with ATT&CK technique T1499.004 for network denial of service attacks. The attack vector involves sending specially crafted TLS traffic with corrupted payloads to a vulnerable OpenSSL instance, which then processes the malformed data and subsequently crashes due to memory corruption or invalid state handling during the decryption process. The impact of this vulnerability extends beyond simple service interruption as it can affect the availability of critical infrastructure components that rely on OpenSSL for secure communications, potentially disrupting business operations and data transmission services. Organizations running affected OpenSSL versions are particularly vulnerable during high-traffic periods when the likelihood of encountering malformed TLS traffic increases. The DoS condition occurs because the cryptographic library fails to properly validate the integrity of the encrypted payload before attempting to process it through the CHACHA20-POLY1305 decryption mechanism. This weakness creates a scenario where an attacker can remotely induce a crash without requiring authentication or advanced exploitation techniques, making it particularly concerning for publicly accessible services that utilize these cipher suites. The vulnerability demonstrates a fundamental flaw in the error recovery mechanisms of the OpenSSL cryptographic library, where the system does not adequately handle corrupted data during the authenticated encryption process, leading to memory corruption and subsequent process termination.
The technical implementation of this vulnerability involves the specific processing of TLS records that contain large payloads when using the CHACHA20-POLY1305 ciphersuite. During the decryption process, the OpenSSL library performs authenticated encryption operations that include both the ChaCha20 stream cipher and the POLY1305 authenticator. When a malformed or corrupted payload is received, the library's handling of the authentication tag validation fails to properly validate the data structure, causing the software to enter an invalid state. This invalid state typically manifests as a memory access violation or buffer overflow condition during the processing of the decryption operations. The vulnerability is particularly pronounced when dealing with larger payloads because the increased data size amplifies the impact of the corrupted data on the internal processing state. The flaw is not exploitable for arbitrary code execution or data theft, but rather represents a straightforward denial of service condition that can be triggered by sending maliciously crafted TLS traffic. The underlying cryptographic implementation does not include proper bounds checking or input validation for the authenticated encryption parameters, allowing corrupted data to propagate through the decryption pipeline until a critical error occurs. This type of vulnerability falls under the category of software faults that can be exploited through carefully constructed inputs to cause system instability, representing a common class of weaknesses in cryptographic libraries where error handling and input validation are insufficient. The vulnerability affects systems that have enabled the CHACHA20-POLY1305 cipher suites in their TLS configurations, which were introduced in OpenSSL 1.1.0 as part of the enhanced security features. These cipher suites were designed to provide forward secrecy and efficient encryption, but the implementation contains a critical flaw in how it handles exceptional conditions during payload processing. The impact is particularly severe for services that depend on OpenSSL for secure communications, as the crash can affect multiple concurrent connections and potentially cause cascading failures in larger network infrastructures. Organizations should consider the broader implications of this vulnerability, as it may be exploited in combination with other network-based attacks to create more sophisticated denial of service scenarios.
Mitigation strategies for CVE-2016-7054 focus primarily on upgrading to OpenSSL version 1.1.0c or later, which contains the necessary patches to address the DoS vulnerability in the CHACHA20-POLY1305 cipher suite implementation. System administrators should prioritize patching affected systems to prevent exploitation, particularly in environments where OpenSSL is used to handle TLS traffic with these specific cipher suites. The upgrade process should include thorough testing to ensure that the patched version does not introduce compatibility issues with existing applications or network configurations. Organizations may also implement network-level mitigations such as rate limiting or traffic filtering to reduce the impact of potential DoS attacks, though these measures do not address the root cause of the vulnerability. Monitoring and logging of TLS connections using CHACHA20-POLY1305 cipher suites can help detect anomalous traffic patterns that might indicate exploitation attempts. Additionally, implementing proper error handling and input validation at the application level can provide an additional layer of defense against malformed TLS traffic. The vulnerability highlights the importance of comprehensive testing of cryptographic libraries, particularly in how they handle edge cases and malformed inputs. Security teams should also consider the broader context of their TLS configurations and potentially disable the CHACHA20-POLY1305 cipher suites if they are not essential for security requirements, while implementing more robust monitoring for TLS traffic. Regular security assessments and vulnerability scanning should include checks for OpenSSL versions and configurations to identify systems at risk. The incident underscores the necessity of maintaining up-to-date cryptographic implementations and the potential consequences of insufficient error handling in security-critical software components. Organizations should also consider implementing automated patch management processes to ensure that security updates are deployed promptly across all affected systems. The vulnerability serves as a reminder of the critical importance of maintaining secure cryptographic implementations and the potential for seemingly minor implementation flaws to create significant availability risks in networked systems.