CVE-2015-8400 in Shell in a Box
Summary
by MITRE
The HTTPS fallback implementation in Shell In A Box (aka shellinabox) before 2.19 makes it easier for remote attackers to conduct DNS rebinding attacks via the "/plain" URL.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 11/11/2024
The vulnerability identified as CVE-2015-8400 resides within the Shell In A Box application, specifically in its HTTPS fallback mechanism that precedes version 2.19. This flaw creates a significant security weakness by allowing remote attackers to exploit DNS rebinding techniques through the "/plain" URL endpoint. Shell In A Box is a web-based terminal emulator that enables users to access shell sessions through a web browser interface, making it a critical component in remote administration and system management environments.
The technical implementation flaw stems from how Shell In A Box handles secure connections when HTTPS is unavailable or fails. When an HTTPS connection cannot be established, the application falls back to HTTP, but this fallback process contains a critical design oversight. The "/plain" URL endpoint, which is intended for unencrypted connections, does not properly validate or restrict access based on the original connection context, creating a pathway for attackers to manipulate DNS resolution and bypass normal security boundaries. This issue is particularly dangerous because it allows an attacker to redirect DNS queries to different IP addresses during the connection process, effectively breaking the security model that should protect against such attacks.
The operational impact of this vulnerability extends beyond simple network reconnaissance, as it enables sophisticated attack vectors that can compromise the integrity of the shell session. Attackers can leverage this weakness to perform DNS rebinding attacks where they manipulate DNS resolution to redirect traffic from legitimate servers to malicious hosts, potentially gaining unauthorized access to system resources or intercepting sensitive data transmitted through the shell interface. The vulnerability affects organizations that rely on Shell In A Box for remote system administration, particularly in environments where HTTPS connectivity is not consistently available or where network security policies do not adequately protect against DNS manipulation techniques.
Security practitioners should consider this vulnerability in relation to CWE-346, which addresses "Origin Validation Error" in the Common Weakness Enumeration catalog, as the flaw represents a failure to properly validate the origin of connection requests during the fallback process. Additionally, this vulnerability aligns with ATT&CK technique T1071.004, which covers "Application Layer Protocol: DNS" and highlights how attackers can manipulate DNS resolution to bypass security controls. Organizations should implement immediate mitigations including upgrading to Shell In A Box version 2.19 or later, implementing proper DNS validation mechanisms, and configuring network-level protections against DNS rebinding attacks. The remediation process should also include reviewing network security policies to ensure that fallback mechanisms do not introduce additional attack surfaces, particularly in environments where shell sessions are accessed from untrusted networks or where the security boundary between different network segments is not properly enforced.