CVE-2018-18508 in Network Security Services
Summary
by MITRE • 10/23/2020
In Network Security Services (NSS) before 3.36.7 and before 3.41.1, a malformed signature can cause a crash due to a null dereference, resulting in a Denial of Service.
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Analysis
by VulDB Data Team • 07/30/2024
The Network Security Services (NSS) library represents a critical component in cryptographic operations across numerous applications and systems, providing essential security functions including SSL/TLS support, certificate handling, and cryptographic operations. This vulnerability affects versions prior to 3.36.7 and 3.41.1, indicating a prolonged period during which systems remained exposed to potential denial of service attacks. The flaw manifests specifically when processing malformed signatures, creating a scenario where the system encounters a null pointer dereference that leads to abrupt termination of the affected process.
The technical root cause of this vulnerability lies in insufficient input validation within the signature processing routines of NSS. When a malformed signature is presented to the system, the cryptographic library fails to properly handle the unexpected data structure, resulting in a null pointer dereference condition. This condition occurs because the code attempts to access memory through a pointer that has not been properly initialized or validated, causing the application to crash immediately. The vulnerability falls under the category of improper input validation as defined by CWE-20, where the system fails to adequately validate or sanitize input data before processing it. This type of error represents a classic null pointer dereference issue that can be exploited to cause system instability and service disruption.
The operational impact of this vulnerability extends beyond simple system crashes, as it creates opportunities for attackers to perform denial of service attacks against systems relying on NSS for cryptographic operations. When exploited, the vulnerability allows an attacker to send specially crafted malformed signatures to services using NSS, causing them to terminate unexpectedly and potentially leading to service unavailability for legitimate users. This type of attack aligns with ATT&CK technique T1499.004, which involves network denial of service attacks through the exploitation of software vulnerabilities. The vulnerability is particularly concerning because it can be triggered through normal cryptographic operations, meaning that any system processing signatures or certificates could be affected without requiring special privileges or complex attack vectors.
Systems utilizing NSS for SSL/TLS operations, certificate validation, or cryptographic signature processing are at risk of this vulnerability. Applications that rely on NSS for security functions include web browsers, email clients, network security appliances, and any software that performs cryptographic signature validation. The vulnerability affects both client and server implementations, making it a widespread concern across the security ecosystem. Organizations should prioritize updating their NSS installations to versions 3.36.7 or 3.41.1, or newer, to mitigate this risk. Additionally, implementing proper input validation mechanisms and monitoring for unusual signature processing patterns can help detect potential exploitation attempts. Network security controls should be configured to limit exposure to potentially malicious signature data, and regular security assessments should verify that systems are running patched versions of the affected library. The vulnerability demonstrates the critical importance of maintaining up-to-date cryptographic libraries and implementing robust input validation practices to prevent exploitation of similar flaws in security-critical software components.