CVE-2017-11697 in Network Security Services
Summary
by MITRE
The __hash_open function in hash.c:229 in Mozilla Network Security Services (NSS) allows context-dependent attackers to cause a denial of service (floating point exception and crash) via a crafted cert8.db file.
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Analysis
by VulDB Data Team • 03/07/2025
The vulnerability identified as CVE-2017-11697 resides within Mozilla Network Security Services NSS library, specifically in the __hash_open function located in hash.c at line 229. This flaw represents a critical denial of service vulnerability that can be exploited by context-dependent attackers through manipulation of certificate database files. The issue manifests when the NSS library processes a crafted cert8.db file, leading to unexpected floating point exceptions and subsequent application crashes. The vulnerability falls under CWE-128, which categorizes improper handling of floating point exceptions, and demonstrates how seemingly benign file processing can result in system instability. The attack vector requires an adversary to prepare a malicious certificate database file that, when processed by NSS, triggers the problematic code path in the hash_open function.
The technical implementation of this vulnerability exploits the lack of proper input validation within the hash table initialization process. When the __hash_open function attempts to parse and process the malicious cert8.db file, it encounters malformed data structures that cause the floating point unit to execute invalid operations. This results in a floating point exception that is not properly handled by the NSS library, leading to an uncontrolled crash of the application or service utilizing the library. The vulnerability demonstrates a classic case of insufficient error handling and input sanitization, where the code fails to anticipate malformed data during database parsing operations. The impact is particularly severe because NSS is widely used across various Mozilla products including Firefox, Thunderbird, and other applications that rely on secure communications.
Operationally, this vulnerability presents significant risks to systems that depend on NSS for certificate management and secure communications. The denial of service condition can affect web browsers, email clients, and server applications that utilize NSS for SSL/TLS operations. Attackers can exploit this weakness by creating specially crafted certificate databases that, when loaded by vulnerable applications, will cause immediate system crashes. The vulnerability can be leveraged in various attack scenarios including web application exploitation, where malicious users might attempt to crash browser sessions or server processes. This type of attack aligns with ATT&CK technique T1499.004, which involves network denial of service attacks through exploitation of application vulnerabilities. The impact extends beyond simple service disruption to potentially enable more sophisticated attacks if combined with other exploitation techniques.
Mitigation strategies for CVE-2017-11697 focus primarily on immediate patching of affected NSS versions, with Mozilla releasing updates that include proper input validation and exception handling for the hash_open function. System administrators should prioritize updating all instances of NSS to patched versions and conduct thorough vulnerability assessments to identify potentially affected applications. Additional protective measures include implementing proper file access controls for certificate databases, monitoring for unusual file modifications, and establishing robust application sandboxing to limit the impact of potential exploitation. Organizations should also consider implementing network segmentation and intrusion detection systems to monitor for exploitation attempts. The vulnerability highlights the importance of proper error handling in cryptographic libraries and demonstrates how seemingly minor implementation flaws can result in significant security implications. Regular security audits and code reviews focusing on input validation and exception handling practices are essential for preventing similar vulnerabilities in security-critical components.