CVE-2012-2385 in mosh
Summary
by MITRE
The terminal dispatcher in mosh before 1.2.1 allows remote authenticated users to cause a denial of service (long loop and CPU consumption) via an escape sequence with a large repeat count value.
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Analysis
by VulDB Data Team • 10/03/2024
The vulnerability identified as CVE-2012-2385 affects mosh version 1.2.1 and earlier, representing a significant security flaw in the terminal dispatcher component of this remote terminal application. Mosh is designed to provide robust remote terminal access with improved performance over traditional ssh connections, but this vulnerability creates a critical weakness that can be exploited by authenticated remote attackers to disrupt service availability. The flaw specifically resides in how mosh processes escape sequences, which are control sequences used to manage terminal behavior and formatting in text-based interfaces.
The technical implementation of this vulnerability stems from inadequate input validation within the terminal dispatcher's handling of escape sequences. When an authenticated user sends a specially crafted escape sequence containing a large repeat count value, the mosh application enters into a prolonged processing loop where it attempts to execute the specified number of repetitions. This flaw manifests as a resource exhaustion attack that consumes excessive cpu cycles and memory resources, effectively creating a denial of service condition. The vulnerability is particularly concerning because it requires only authentication to exploit, meaning that any authenticated user with access to the mosh session can potentially trigger this condition without requiring additional privileges or complex attack vectors.
The operational impact of CVE-2012-2385 extends beyond simple service disruption, as it can affect the entire availability and performance of mosh sessions. Attackers can leverage this vulnerability to consume system resources, potentially causing legitimate users to experience degraded performance or complete service unavailability. The long-running loop characteristic of this vulnerability means that the system remains compromised until the process is manually terminated or the system is rebooted, creating extended periods of service disruption. This type of vulnerability is classified under CWE-770, which deals with allocation of resources without limits or with inadequate limits, and aligns with ATT&CK technique T1499.004 for network denial of service attacks. The vulnerability represents a classic example of a resource exhaustion attack that can be executed with relatively simple input manipulation.
Mitigation strategies for this vulnerability require immediate patching of mosh installations to version 1.2.1 or later, where the developers have implemented proper input validation and repeat count limiting mechanisms. Organizations should also consider implementing monitoring solutions that can detect unusual cpu consumption patterns or resource usage spikes that may indicate exploitation attempts. Network administrators should review access controls to limit authentication privileges where possible, and implement rate limiting or input sanitization measures at network boundaries. The fix typically involves implementing bounds checking on repeat count values within escape sequences, ensuring that maximum values are enforced to prevent the execution of excessively long loops. Additionally, system administrators should conduct regular security assessments of terminal applications and maintain updated threat intelligence to identify similar vulnerabilities in other network services that may be susceptible to similar resource exhaustion attacks.