CVE-2003-0795 in Quagga
Summary
by MITRE
The vty layer in Quagga before 0.96.4, and Zebra 0.93b and earlier, does not verify that sub-negotiation is taking place when processing the SE marker, which allows remote attackers to cause a denial of service (crash) via a malformed telnet command to the telnet CLI port, which may trigger a null dereference.
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Analysis
by VulDB Data Team • 10/03/2024
The vulnerability identified as CVE-2003-0795 affects the vty layer implementation in Quagga routing software versions prior to 0.96.4 and Zebra versions 0.93b and earlier. This represents a critical security flaw in network infrastructure software that manages routing protocols and provides command line interfaces for network device configuration. The affected systems include various routing daemons that utilize the vty (virtual terminal) layer for remote management through telnet connections, making this vulnerability particularly dangerous in enterprise and service provider network environments where these components are widely deployed.
The technical flaw resides in the improper validation of telnet protocol negotiation sequences within the vty layer implementation. Specifically, when processing the SE (Subnegotiation End) marker in telnet command sequences, the software fails to verify that proper sub-negotiation has occurred before proceeding with further processing. This validation gap creates a condition where malformed telnet commands can be processed without adequate checks, leading to memory corruption issues. The vulnerability manifests as a null pointer dereference when the system attempts to access memory locations that have not been properly initialized or allocated during the telnet command parsing process.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can result in complete system crashes and service interruptions for network devices running affected versions of Quagga or Zebra. Network administrators managing critical infrastructure components that rely on these routing protocols face significant risk of unauthorized service disruption attacks that could compromise network availability and reliability. The vulnerability is particularly concerning because it can be exploited remotely through the telnet CLI port, requiring no authentication credentials to trigger the malicious behavior. This makes it an attractive target for automated scanning and exploitation campaigns targeting network infrastructure devices.
The flaw aligns with CWE-476, which describes null pointer dereference conditions, and represents a classic example of improper input validation in network protocol handling. From an attack perspective, this vulnerability maps to ATT&CK technique T1210, which involves exploiting weaknesses in remote services through malformed input. The vulnerability demonstrates poor defensive programming practices where the software assumes proper protocol negotiation has occurred without implementing adequate verification mechanisms. Organizations using these networking components should prioritize immediate patching to address the vulnerability, as the impact extends to all network devices that expose telnet management interfaces and rely on the affected Quagga or Zebra implementations for routing functionality. The security implications underscore the importance of proper protocol validation and memory management in network infrastructure software to prevent exploitation leading to service disruption and potential network compromise.