CVE-2009-4923 in ASA 5580
Summary
by MITRE
Unspecified vulnerability in the DTLS implementation on Cisco Adaptive Security Appliances (ASA) 5580 series devices with software before 8.1(2) allows remote attackers to cause a denial of service (traceback) via TLS fragments, aka Bug ID CSCso53162.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 04/20/2017
The vulnerability identified as CVE-2009-4923 affects Cisco Adaptive Security Appliances (ASA) 5580 series devices operating with software versions prior to 8.1(2). This represents a critical flaw within the Datagram Transport Layer Security (DTLS) implementation that enables remote attackers to execute denial of service attacks. The vulnerability manifests specifically when the ASA device processes TLS fragments, creating a traceback condition that can disrupt normal network operations and potentially lead to complete service unavailability. The issue stems from inadequate handling of malformed or unexpected DTLS packet fragments within the security appliance's protocol processing stack.
The technical nature of this vulnerability resides in the improper validation and processing of DTLS fragments within the ASA's security software implementation. When remote attackers send specially crafted TLS fragments to the affected devices, the system fails to properly handle these malformed packets, resulting in a traceback condition that causes the device to enter an unstable state. This behavior aligns with CWE-129, which addresses improper validation of input boundaries, and demonstrates how insufficient input sanitization can lead to system instability. The flaw essentially allows an attacker to exploit the device's DTLS processing logic through carefully constructed network traffic that triggers an internal error condition, causing the appliance to malfunction or crash.
From an operational impact perspective, this vulnerability presents a significant risk to network security infrastructure as it allows remote attackers to disrupt critical security services without requiring authentication or privileged access. The denial of service condition affects the availability of network security services provided by the ASA 5580 series devices, potentially leaving network segments unprotected against threats. Organizations relying on these security appliances for network protection face the risk of extended service outages that could compromise their overall security posture. The traceback condition may also result in system instability that could be exploited further, making the vulnerability particularly dangerous in environments where network availability is critical. This aligns with ATT&CK technique T1499.004, which covers network denial of service attacks that target infrastructure components.
The mitigation strategy for this vulnerability requires immediate deployment of Cisco's security advisory and software updates to version 8.1(2) or later, which contain the necessary patches to address the DTLS implementation flaw. Network administrators should also implement additional monitoring and logging to detect suspicious traffic patterns that may indicate exploitation attempts. Organizations should consider implementing network segmentation and access controls to limit exposure of affected devices to untrusted networks. The patch addresses the root cause by improving input validation and error handling within the DTLS processing code, preventing malformed fragments from triggering the traceback condition. Security teams should also conduct thorough vulnerability assessments to identify all affected ASA devices within their network infrastructure and prioritize remediation efforts based on risk exposure and business criticality.