CVE-2017-5334 in GnuTLS
Summary
by MITRE
Double free vulnerability in the gnutls_x509_ext_import_proxy function in GnuTLS before 3.3.26 and 3.5.x before 3.5.8 allows remote attackers to have unspecified impact via crafted policy language information in an X.509 certificate with a Proxy Certificate Information extension.
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Analysis
by VulDB Data Team • 10/28/2022
The vulnerability identified as CVE-2017-5334 represents a critical double free condition within the GnuTLS cryptographic library's handling of X.509 certificates containing Proxy Certificate Information extensions. This flaw exists in GnuTLS versions prior to 3.3.26 and 3.5.x versions before 3.5.8, making a substantial portion of deployed cryptographic implementations susceptible to exploitation. The double free vulnerability occurs during the processing of certificate extensions when the gnutls_x509_ext_import_proxy function fails to properly manage memory allocation and deallocation sequences, creating opportunities for memory corruption that can be leveraged by remote attackers.
The technical exploitation of this vulnerability involves crafting malicious X.509 certificates with specifically formatted Proxy Certificate Information extensions that trigger the flawed memory management logic. When the vulnerable GnuTLS library processes such certificates, the double free condition manifests through improper handling of memory pointers during the certificate extension parsing phase. This flaw is classified as a CWE-415 Double Free vulnerability, which occurs when a program frees the same memory block twice, leading to undefined behavior and potential memory corruption. The attack vector is remote, meaning that an attacker can exploit this vulnerability without requiring local access to the target system, simply by presenting a malicious certificate to a vulnerable GnuTLS implementation.
The operational impact of CVE-2017-5334 extends across numerous security-sensitive applications and systems that rely on GnuTLS for SSL/TLS communications and certificate validation. This includes web servers, email servers, VPN implementations, and any software components that depend on GnuTLS for secure communications. The unspecified impact mentioned in the vulnerability description can encompass arbitrary code execution, denial of service conditions, or information disclosure, depending on how the memory corruption manifests during exploitation. Attackers could potentially execute malicious code on vulnerable systems or cause service interruptions that compromise the availability of secure communications. The vulnerability affects systems where GnuTLS is used for certificate validation, particularly in scenarios involving certificate chain verification and proxy certificate processing.
Mitigation strategies for CVE-2017-5334 primarily focus on upgrading affected GnuTLS implementations to versions that contain the necessary patches. System administrators should immediately update to GnuTLS 3.3.26 or 3.5.8 and later versions where the double free condition has been resolved through proper memory management practices. Additionally, organizations should implement certificate validation policies that limit the acceptance of certificates with Proxy Certificate Information extensions when such extensions are not required for legitimate operations. Network monitoring should be enhanced to detect unusual certificate processing patterns that might indicate exploitation attempts. From an ATT&CK perspective, this vulnerability maps to techniques involving memory corruption and privilege escalation, as attackers could leverage the double free condition to gain elevated privileges or execute arbitrary code within the context of vulnerable applications. Security teams should also consider implementing certificate pinning mechanisms and certificate transparency monitoring to reduce the attack surface and detect malicious certificates more effectively.