CVE-2018-10845 in GnuTLS
Summary
by MITRE
It was found that the GnuTLS implementation of HMAC-SHA-384 was vulnerable to a Lucky thirteen style attack. Remote attackers could use this flaw to conduct distinguishing attacks and plain text recovery attacks via statistical analysis of timing data using crafted packets.
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Analysis
by VulDB Data Team • 05/04/2023
The vulnerability identified as CVE-2018-10845 represents a critical weakness in the GnuTLS cryptographic library's implementation of HMAC-SHA-384 algorithm. This flaw exposes systems using GnuTLS to sophisticated timing-based attacks that exploit subtle variations in processing time to infer sensitive information. The vulnerability specifically affects the cryptographic implementation's resistance to side-channel attacks, creating opportunities for adversaries to perform statistical analysis on timing data collected during cryptographic operations.
The technical nature of this vulnerability stems from the implementation's failure to provide constant-time execution for HMAC-SHA-384 operations. Attackers can leverage the Lucky Thirteen attack pattern, which targets cryptographic implementations that exhibit timing variations based on input data. This particular attack style exploits the fact that different input values can cause the cryptographic processor to take varying amounts of time to complete operations, creating measurable timing differences that can be statistically analyzed to recover plaintext information.
The operational impact of this vulnerability extends beyond simple data confidentiality breaches, as it enables adversaries to perform distinguishing attacks that can differentiate between different types of encrypted data. Remote attackers can craft specific packets that, when processed by vulnerable GnuTLS implementations, reveal enough timing information to reconstruct portions of the original plaintext. This capability represents a significant threat to secure communications, particularly in environments where sensitive data is transmitted over networks using GnuTLS-based encryption.
Systems utilizing GnuTLS for secure communications are particularly at risk when they process untrusted network traffic that could be manipulated by attackers to trigger timing variations. The vulnerability affects any application or service that relies on GnuTLS for TLS/SSL connections, including web servers, email servers, and other network services that implement cryptographic protocols. Organizations using affected versions of GnuTLS should prioritize immediate remediation to prevent potential exploitation that could lead to complete cryptographic breakdown and unauthorized data access.
This vulnerability aligns with CWE-327, which addresses the use of weak cryptographic algorithms and improper implementation of cryptographic functions. The attack pattern corresponds to techniques documented in the ATT&CK framework under T1552.001, specifically targeting credential access through cryptographic attacks. The Lucky Thirteen attack vector demonstrates how seemingly minor implementation flaws in cryptographic libraries can create substantial security risks, highlighting the critical importance of constant-time algorithm implementations and proper side-channel attack mitigation in cryptographic software development.
Mitigation strategies for this vulnerability require immediate patching of affected GnuTLS versions and implementation of proper timing attack resistance measures. Organizations should ensure their cryptographic libraries are updated to versions that provide constant-time execution for HMAC operations and implement additional monitoring to detect potential timing-based attacks. System administrators should also consider implementing network-level protections and additional cryptographic validation mechanisms to detect and prevent exploitation attempts targeting this specific vulnerability pattern.