CVE-2019-1697 in ASA
Summary
by MITRE
A vulnerability in the implementation of the Lightweight Directory Access Protocol (LDAP) feature in Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerabilities are due to the improper parsing of LDAP packets sent to an affected device. An attacker could exploit these vulnerabilities by sending a crafted LDAP packet, using Basic Encoding Rules (BER), to be processed by an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.
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Analysis
by VulDB Data Team • 09/12/2023
The vulnerability identified as CVE-2019-1697 represents a critical denial of service weakness within Cisco's Adaptive Security Appliance and Firepower Threat Defense software implementations. This flaw specifically targets the Lightweight Directory Access Protocol functionality that is integral to enterprise security infrastructure, affecting devices running Cisco ASA Software version 9.0 through 9.8 and FTD Software version 6.0 through 6.4. The vulnerability stems from inadequate input validation mechanisms within the LDAP packet processing pipeline, creating a scenario where malformed packets can trigger unexpected device behavior. The issue manifests when devices receive specially crafted LDAP packets encoded using Basic Encoding Rules, which are standard protocols for representing data structures in directory services environments.
The technical exploitation of this vulnerability occurs through the improper parsing of LDAP packets that contain malformed or unexpected data sequences. When an affected device processes these crafted packets, the flawed LDAP implementation fails to properly handle the packet structure, leading to memory corruption or unexpected state transitions that ultimately result in device restart. This behavior aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which covers heap-based buffer overflow scenarios. The vulnerability specifically exploits the lack of proper bounds checking and input sanitization within the LDAP processing module, allowing attackers to manipulate the device's normal operational flow through carefully constructed packet payloads.
From an operational perspective, this vulnerability presents a significant risk to enterprise network security infrastructure, as it enables remote attackers to disrupt critical network services without requiring authentication credentials. The denial of service condition impacts availability of security services that organizations rely upon for network protection, potentially leaving networks vulnerable to other attacks during the device restart period. The attack vector is particularly concerning as it requires no privileged access and can be executed from any network location capable of reaching the affected device. This vulnerability directly maps to ATT&CK technique T1499.004, which involves network denial of service attacks, and represents a critical weakness in the security infrastructure that could be exploited to undermine network resilience and availability.
Organizations should implement immediate mitigations including disabling LDAP functionality on affected devices when not required, implementing network segmentation to limit access to LDAP ports, and applying Cisco's recommended software patches that address the specific parsing flaws in the LDAP implementation. Network administrators should also consider deploying intrusion detection systems capable of identifying and blocking malformed LDAP packets, while monitoring for unusual device restart patterns that could indicate exploitation attempts. The vulnerability underscores the importance of proper input validation and the need for robust error handling in security appliances, as it demonstrates how a single parsing flaw can result in complete service disruption. Additionally, organizations should review their overall network security posture to ensure that critical infrastructure devices are properly hardened against remote exploitation attempts.