CVE-2021-20108 in Asset Explorer Agent
Summary
by MITRE • 07/19/2021
Manage Engine Asset Explorer Agent 1.0.34 listens on port 9000 for incoming commands over HTTPS from Manage Engine Server. The HTTPS certificates are not verified which allows any arbitrary user on the network to send commands over port 9000. While these commands may not be executed (due to authtoken validation), the Asset Explorer agent will reach out to the manage engine server for an HTTP request. During this process, AEAgent.cpp allocates 0x66 bytes using "malloc". This memory is never free-ed in the program, causing a memory leak. Additionally, the instruction sent to aeagent (ie: NEWSCAN, DELTASCAN, etc) is converted to a unicode string, but is never freed. These memory leaks allow a remote attacker to exploit a Denial of Service scenario through repetitively sending these commands to an agent and eventually crashing it the agent due to an out-of-memory condition.
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Analysis
by VulDB Data Team • 07/22/2021
The vulnerability identified as CVE-2021-20108 affects Manage Engine Asset Explorer Agent version 1.0.34, presenting a significant security flaw that combines authentication bypass with memory management issues. This agent operates by listening on port 9000 for HTTPS commands originating from the Manage Engine Server, creating a potential attack surface where unauthenticated network users can interact with the system. The absence of HTTPS certificate verification represents a fundamental security weakness that allows any remote attacker to send commands to the agent without proper authentication, violating standard security practices for secure communication channels.
The technical implementation of this vulnerability manifests through multiple memory management flaws that compound the security risk. During command processing, the AEAgent.cpp component allocates 102 bytes of memory using malloc but fails to properly free this allocation, creating a persistent memory leak. This memory leak occurs each time commands such as NEWSCAN or DELTASCAN are received and processed, with the unicode string conversions of these commands also not being properly deallocated. The vulnerability specifically aligns with CWE-401, which addresses improper release of memory, and demonstrates how repeated exploitation can lead to system instability. The agent's failure to manage memory resources properly creates a cumulative effect where each processed command adds to the growing memory consumption without cleanup.
The operational impact of this vulnerability extends beyond simple authentication bypass to create a reliable Denial of Service condition. Attackers can repeatedly send malicious commands to the agent, causing continuous memory allocation without corresponding deallocation, ultimately leading to memory exhaustion and system crash. This scenario represents a classic resource exhaustion attack pattern that aligns with ATT&CK technique T1499.004, which covers resource exhaustion attacks. The vulnerability creates a persistent condition where the agent becomes increasingly unstable over time, making it unreliable for legitimate asset management operations. Network administrators may experience intermittent service disruptions or complete system failures, particularly in environments where the agent is frequently exposed to network traffic.
Mitigation strategies for this vulnerability should address both the authentication bypass and memory management issues. Immediate remediation involves applying the vendor-provided security patches or upgrading to versions that implement proper HTTPS certificate verification and memory cleanup mechanisms. Network segmentation should be implemented to restrict access to port 9000, limiting exposure to trusted networks only. Additionally, monitoring systems should be deployed to detect unusual command patterns or memory usage spikes that could indicate exploitation attempts. The vulnerability demonstrates the importance of proper resource management in security-critical applications and highlights the need for comprehensive testing of memory allocation and deallocation patterns in server-side components. Organizations should also consider implementing intrusion detection systems that can identify and alert on suspicious command sequences targeting this specific port and protocol combination, ensuring that the memory leak vulnerability cannot be exploited for sustained disruption of asset management services.