CVE-2015-3308 in GnuTLS
Summary
by MITRE
Double free vulnerability in lib/x509/x509_ext.c in GnuTLS before 3.3.14 allows remote attackers to cause a denial of service or possibly have unspecified other impact via a crafted CRL distribution point.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 05/09/2022
The vulnerability identified as CVE-2015-3308 represents a critical double free condition within the GNU TLS library's X.509 certificate handling mechanism. This flaw exists in the x509_ext.c file and affects versions prior to 3.3.14, creating a scenario where remote attackers can manipulate the library's memory management routines through carefully crafted certificate revocation lists. The double free vulnerability occurs when the same memory block is freed twice during the processing of a Certificate Revocation List distribution point, leading to unpredictable behavior in the application's memory heap management.
The technical exploitation of this vulnerability leverages the improper handling of X.509 extension parsing within the GNU TLS implementation. When processing a maliciously constructed CRL distribution point, the library fails to properly validate the structure of the extension data, resulting in a scenario where memory allocation functions are called multiple times for the same memory segment. This condition violates fundamental memory safety principles and creates opportunities for attackers to manipulate the heap state. The vulnerability maps directly to CWE-415, which specifically addresses double free conditions in memory management, and aligns with ATT&CK technique T1059.007 for remote code execution through memory corruption.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially enable more sophisticated attacks depending on the environment where GNU TLS is deployed. While the primary effect manifests as denial of service, the underlying memory corruption could theoretically allow for arbitrary code execution or information disclosure if the attacker can control the memory layout sufficiently. Systems utilizing GNU TLS for secure communications, including web servers, email servers, and VPN implementations, become vulnerable to this attack vector. The vulnerability's remote nature means that attackers do not require local access to exploit the flaw, making it particularly dangerous in networked environments where certificate validation occurs automatically.
Mitigation strategies for CVE-2015-3308 focus primarily on immediate version upgrades to GNU TLS 3.3.14 or later, which contain the necessary patches to prevent the double free condition. Organizations should also implement network segmentation and monitoring to detect anomalous certificate processing behavior that might indicate exploitation attempts. The patch addresses the root cause by introducing proper validation of extension data structures before memory allocation occurs, ensuring that the same memory block cannot be freed multiple times during the certificate processing lifecycle. Additionally, system administrators should conduct thorough vulnerability assessments of all systems using GNU TLS to identify potential exposure and implement comprehensive patch management procedures to prevent similar issues from arising in the future.