CVE-2013-4487 in GnuTLS
Summary
by MITRE
Off-by-one error in the dane_raw_tlsa in the DANE library (libdane) in GnuTLS 3.1.x before 3.1.16 and 3.2.x before 3.2.6 allows remote servers to cause a denial of service (memory corruption) via a response with more than four DANE entries. NOTE: this issue is due to an incomplete fix for CVE-2013-4466.
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Analysis
by VulDB Data Team • 12/25/2024
The vulnerability identified as CVE-2013-4487 represents a critical off-by-one error within the DANE library component of GnuTLS, specifically affecting versions prior to 3.1.16 and 3.2.6. This flaw manifests in the dane_raw_tlsa function which processes DANE (DNS-based Authentication of Named Entities) entries during TLS certificate verification processes. The issue arises from inadequate boundary checking when handling DNS responses containing DANE records, creating a scenario where memory corruption can occur through carefully crafted malicious responses. The vulnerability specifically targets scenarios where remote servers provide DNS responses containing more than four DANE entries, exploiting a logical error that was introduced as an incomplete remediation for the previously disclosed CVE-2013-4466, demonstrating the complexity of security patching in cryptographic libraries.
The technical implementation of this vulnerability stems from improper array bounds checking within the DANE processing logic. When the dane_raw_tlsa function receives DNS responses with excessive DANE entries, the off-by-one error causes memory access violations that can lead to buffer overflows or memory corruption patterns. This type of flaw falls under CWE-129, which addresses insufficient boundary checking, and more specifically aligns with CWE-121, concerning buffer overflow conditions. The error occurs during the parsing of TLSA (Transport Layer Security Authentication) records in DNS responses, where the library assumes a maximum of four entries but fails to properly validate or handle responses exceeding this limit. This memory corruption vulnerability can be exploited by remote attackers who control DNS servers or have the ability to manipulate DNS responses, potentially leading to arbitrary code execution or complete service disruption.
The operational impact of CVE-2013-4487 extends beyond simple denial of service, as the memory corruption can result in unpredictable behavior throughout the GnuTLS library. Systems utilizing GnuTLS for secure communications, particularly those implementing DANE-based certificate validation, become vulnerable to attacks that can compromise the integrity of TLS connections. The vulnerability affects applications that rely on GnuTLS for certificate verification, including web servers, email clients, and other network services that implement DANE security measures. Attackers can leverage this flaw by crafting DNS responses with excessive DANE entries, causing the vulnerable GnuTLS library to corrupt memory structures, potentially leading to application crashes, data corruption, or in more severe cases, execution of arbitrary code within the context of the affected application. The incomplete nature of the original fix for CVE-2013-4466 means that organizations implementing the initial patches may still remain vulnerable to this specific memory corruption scenario.
Mitigation strategies for CVE-2013-4487 require immediate patching of affected GnuTLS installations to versions 3.1.16 or 3.2.6 and later, which contain proper boundary checking implementations. System administrators should prioritize updating all systems that utilize GnuTLS libraries, particularly those implementing DANE certificate validation. Additionally, network monitoring should be enhanced to detect unusual DNS responses containing excessive DANE entries, serving as an early warning mechanism for potential exploitation attempts. Organizations may also consider implementing DNS security measures such as DNSSEC validation to prevent DNS spoofing attacks that could leverage this vulnerability. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation through memory corruption and denial of service attacks, specifically targeting the credential access and impact phases. The vulnerability demonstrates the importance of thorough regression testing when implementing security patches, as the incomplete fix for CVE-2013-4466 created this subsequent vulnerability, highlighting the need for comprehensive security validation processes in cryptographic library maintenance and updates.