CVE-2019-3836 in GnuTLS
Summary
by MITRE
It was discovered in gnutls before version 3.6.7 upstream that there is an uninitialized pointer access in gnutls versions 3.6.3 or later which can be triggered by certain post-handshake messages.
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Analysis
by VulDB Data Team • 08/21/2023
The vulnerability identified as CVE-2019-3836 resides within the gnutls library, a critical component for secure communications in numerous applications and systems. This issue manifests as an uninitialized pointer access that affects gnutls versions 3.6.3 and later, with the vulnerability only being fully addressed in version 3.6.7 and subsequent releases. The flaw specifically emerges during processing of certain post-handshake messages, which are part of the tls protocol negotiation process that occurs after the initial handshake has been completed. This type of vulnerability represents a significant security concern as it can potentially be exploited to disrupt service availability or gain unauthorized access to systems relying on gnutls for secure communication.
The technical implementation of this vulnerability stems from improper initialization of memory pointers within the gnutls library's handling of post-handshake operations. When processing specific post-handshake messages, the library fails to properly initialize certain pointer variables before utilizing them, leading to potential memory access violations. This uninitialized pointer access creates a condition where the program may attempt to read from or write to memory locations that have not been properly allocated or initialized, potentially causing program crashes or unpredictable behavior. The vulnerability operates at the application layer within the tls implementation and specifically affects the library's ability to process certain message types that are part of the tls 1.3 protocol specification, making it particularly dangerous in environments where tls 1.3 is actively utilized.
The operational impact of CVE-2019-3836 extends beyond simple service disruption, as it represents a potential vector for more sophisticated attacks within the context of the attack chain. From an operational security perspective, systems utilizing gnutls versions 3.6.3 through 3.6.6 are vulnerable to denial of service attacks that can cause applications to crash or become unresponsive. The vulnerability's classification aligns with CWE-457, which describes "Use of Uninitialized Variable," and represents a specific instance of uninitialized memory access that can lead to information disclosure or remote code execution under certain conditions. Security professionals must consider this vulnerability in the context of the MITRE ATT&CK framework, particularly within the execution and privilege escalation phases where such memory corruption vulnerabilities can be leveraged to gain unauthorized access to systems. The impact is particularly severe in server environments where gnutls is used to secure web applications, email services, and other critical infrastructure components.
Mitigation strategies for CVE-2019-3836 primarily focus on immediate version updates to gnutls 3.6.7 or later, which contain the necessary patches to address the uninitialized pointer access issue. Organizations should prioritize patching all systems and applications that depend on gnutls, particularly those handling sensitive data or operating in high-security environments. Additional defensive measures include implementing network segmentation to limit exposure, monitoring for unusual connection patterns that might indicate exploitation attempts, and conducting thorough vulnerability assessments to identify all systems utilizing affected gnutls versions. Security teams should also consider implementing intrusion detection systems that can identify anomalous behavior consistent with tls protocol manipulation attempts, as the vulnerability's exploitation may not always result in immediate crashes but could be used to gradually compromise system integrity. The remediation process should also include verifying that all dependent applications and services have been properly updated to ensure complete protection against this specific vulnerability.