CVE-2014-9424 in LibreSSL
Summary
by MITRE
Double free vulnerability in the ssl_parse_clienthello_use_srtp_ext function in d1_srtp.c in LibreSSL before 2.1.2 allows remote attackers to cause a denial of service or possibly have unspecified other impact by triggering a certain length-verification error during processing of a DTLS handshake.
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Analysis
by VulDB Data Team • 03/01/2022
The vulnerability identified as CVE-2014-9424 represents a critical double free condition within the LibreSSL cryptographic library implementation. This flaw exists specifically within the ssl_parse_clienthello_use_srtp_ext function located in the d1_srtp.c file, affecting LibreSSL versions prior to 2.1.2. The double free vulnerability occurs during the processing of DTLS handshakes when a particular length-verification error is triggered, creating a scenario where memory allocated for SRTP extension processing is freed twice, potentially leading to memory corruption and system instability. The issue manifests during the parsing of client hello messages in DTLS connections, where the library fails to properly validate extension lengths before proceeding with memory allocation and deallocation operations. This type of vulnerability falls under CWE-415, which specifically addresses double free conditions in software implementations, and represents a classic heap corruption vulnerability that can be exploited remotely without requiring authentication or privileged access. The vulnerability is particularly concerning in networked environments where DTLS services are exposed to untrusted clients, as it can be triggered through malformed handshake messages that manipulate the expected extension lengths.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enabling more sophisticated attacks depending on the environment and system configuration. When exploited, the double free condition can cause the targeted service to crash and restart, leading to persistent denial of service conditions that can be difficult to detect and mitigate. However, the potential for more severe consequences exists, as the memory corruption resulting from the double free could potentially be leveraged to execute arbitrary code or escalate privileges if the vulnerable system is running with elevated privileges. The vulnerability affects DTLS implementations that utilize SRTP (Secure Real-time Transport Protocol) extensions, which are commonly used in VoIP applications, video conferencing systems, and other real-time communication services that require secure media transmission. Attackers can craft malicious DTLS client hello messages with carefully constructed SRTP extension data that triggers the length verification error, causing the vulnerable LibreSSL implementation to free the same memory block twice, potentially corrupting the heap structure and leading to unpredictable behavior. This vulnerability directly impacts the integrity of the SSL/TLS stack and can compromise the availability and potentially confidentiality of secure communications, particularly in environments where DTLS services are critical to business operations.
Mitigation strategies for CVE-2014-9424 focus primarily on upgrading to patched versions of LibreSSL, specifically version 2.1.2 or later, which contains the necessary fixes to prevent the double free condition from occurring. System administrators should prioritize patching affected systems, particularly those running DTLS services or applications that depend on LibreSSL for secure communications. Additionally, network administrators can implement defensive measures such as rate limiting and connection monitoring to detect and block anomalous DTLS handshake patterns that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper memory management in cryptographic libraries and highlights the need for comprehensive input validation and error handling in security-critical code. Organizations should also consider implementing intrusion detection systems that can monitor for unusual DTLS handshake behaviors and potential exploitation attempts. Given that this vulnerability operates at the protocol level within the SSL/TLS stack, the fix requires careful attention to the memory allocation and deallocation logic in the specific function where the issue occurs, ensuring that extension data is properly validated before any memory operations are performed. The remediation process should include thorough testing of patched implementations to ensure that the fix does not introduce regressions in legitimate DTLS functionality while effectively preventing the double free condition from being exploited by remote attackers.