CVE-2017-17099 in SyncBreeze Enterprise
Summary
by MITRE
There exists an unauthenticated SEH based Buffer Overflow vulnerability in the HTTP server of Flexense SyncBreeze Enterprise v10.1.16. When sending a GET request with an excessive length, it is possible for a malicious user to overwrite the SEH record and execute a payload that would run under the Windows SYSTEM account.
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Analysis
by VulDB Data Team • 12/12/2019
The vulnerability identified as CVE-2017-17099 represents a critical buffer overflow flaw within the HTTP server component of Flexense SyncBreeze Enterprise version 10.1.16. This issue manifests as an unauthenticated stack-based buffer overflow that occurs during HTTP request processing, specifically when handling GET requests containing excessively long input data. The vulnerability falls under the Common Weakness Enumeration category CWE-121, which describes stack-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations including the structured exception handler (SEH) chain.
The technical implementation of this vulnerability exploits the lack of proper input validation within the HTTP server's request parsing mechanism. When a maliciously crafted GET request is sent to the vulnerable service, the application fails to properly validate the length of the request data before processing it. This allows an attacker to supply input data that exceeds the allocated buffer space, causing a stack overflow condition that ultimately corrupts the SEH record. The SEH mechanism in windows operates by maintaining a linked list of exception handlers, and when this chain is overwritten, it provides an attacker with the opportunity to redirect execution flow to malicious code.
The operational impact of this vulnerability is severe as it enables remote code execution with elevated privileges. The vulnerability specifically allows execution under the Windows SYSTEM account, which represents the highest privilege level available in the Windows operating system. This privilege escalation capability means that successful exploitation would grant an attacker complete control over the affected system, enabling them to install malware, modify system files, access sensitive data, or establish persistence mechanisms. The unauthenticated nature of the vulnerability further compounds the risk as any external attacker can exploit this without requiring valid credentials.
From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1059.007 for command and script interpreter, as exploitation would likely involve executing malicious payloads through the compromised HTTP server. The vulnerability also maps to T1068 for exploit for privilege escalation, since the payload execution occurs with SYSTEM privileges. Security professionals should note that this vulnerability represents a classic example of improper input validation leading to memory corruption, which is a common attack vector in network services. The attack surface is particularly concerning for enterprise environments where SyncBreeze servers might be exposed to untrusted networks or internet-facing services.
Mitigation strategies should focus on immediate patching of the affected software version, as Flexense has released updates to address this specific vulnerability. Network segmentation and firewall rules should be implemented to restrict access to the SyncBreeze HTTP server from untrusted networks. Additionally, implementing intrusion detection systems that monitor for anomalous HTTP request patterns and excessive data lengths can help detect potential exploitation attempts. The vulnerability demonstrates the importance of proper input validation and bounds checking in network service implementations, and serves as a reminder that even enterprise-grade software can contain critical flaws that require immediate attention. Organizations should also consider implementing application whitelisting and privilege separation mechanisms to limit the potential impact of successful exploitation attempts, while maintaining comprehensive monitoring and logging of HTTP server activities to detect unauthorized access attempts.