CVE-2005-1566 in WLAN AP ADSL Router
Summary
by MITRE
Acrowave AAP-3100AR wireless router allows remote attackers to bypass authentication by pressing CTRL-C at the username or password prompt in a telnet session, which causes the shell to crash and restart, then leave the user in the new shell.
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Analysis
by VulDB Data Team • 07/23/2017
The CVE-2005-1566 vulnerability affects the Acrowave AAP-3100AR wireless router, representing a critical authentication bypass flaw that stems from improper handling of telnet session interactions. This vulnerability exploits a fundamental design weakness in the router's command-line interface where the system fails to properly validate or sanitize user input during the authentication process. When an attacker establishes a telnet connection to the device and presses CTRL-C at either the username or password prompt, the system's response mechanism becomes compromised, leading to an unexpected shell termination and restart that leaves the attacker in an unauthenticated shell environment.
The technical exploitation of this vulnerability demonstrates a classic case of improper input handling and signal processing within embedded network devices. The router's telnet service does not adequately protect against interrupt signals during authentication phases, allowing malicious actors to manipulate the authentication flow through simple keyboard interrupts. This behavior creates an unintended access path that bypasses the normal authentication mechanisms entirely, effectively granting remote attackers administrative privileges without proper credentials. The vulnerability is particularly concerning as it operates at the protocol level where legitimate administrative access would normally require proper authentication.
From an operational perspective, this vulnerability presents a significant risk to network security infrastructure as it allows remote attackers to gain administrative access to wireless routers without knowledge of valid credentials. The impact extends beyond simple unauthorized access, as administrators may be unaware that their devices have been compromised, especially if the shell restart occurs silently or without clear error messages. The vulnerability is particularly dangerous in environments where wireless routers serve as primary network gateways, as it could enable attackers to modify firewall rules, redirect traffic, or establish persistent backdoors within the network infrastructure.
Security professionals should consider this vulnerability in the context of the CWE-248 weakness category, which addresses "Uncaught Exception" conditions in software systems. The router's failure to properly handle the CTRL-C interrupt signal represents an unhandled exception that leads to an insecure state rather than a graceful error recovery. Additionally, this vulnerability aligns with ATT&CK technique T1021.001 for remote services and T1078 for valid accounts, as it enables unauthorized access through legitimate remote access protocols while potentially creating persistent access paths. The vulnerability also reflects poor input validation practices that could be addressed through proper signal handling, authentication flow management, and robust error recovery mechanisms.
The recommended mitigations for CVE-2005-1566 include immediate firmware updates from Acrowave if available, or implementing network segmentation to isolate affected routers from critical network segments. Network administrators should disable telnet access and migrate to SSH-based management protocols where possible, as SSH provides better protection against such interrupt-based attacks. Additionally, implementing proper logging and monitoring of authentication attempts can help detect exploitation attempts. The vulnerability highlights the importance of secure coding practices in embedded systems, particularly regarding signal handling and exception management, and demonstrates why network device vendors must implement proper security testing throughout their development lifecycle. Organizations should also consider implementing network access control lists and intrusion detection systems to monitor for unusual telnet activity or shell restart patterns that might indicate exploitation attempts.